Throughout Suckin' Grits on Route 66, I've have various "hall of mirrors" type problems, commonly on signs such as at the start of Camp Crystal Lake but most notably now on Bigfoot Convention.
Until this point, it was simply a nuisance, but given the severity of the problem on this level and how it drastically ramps up the difficulty of the game, I figured it might be time to see if anyone else has encountered the problem and/or knows of a work around. Seems like it can't find the wall sprites that it's looking for, but I've been experiencing a couple of other random problems, such as the blue Vixens no longer attacking me; they simply float around, impervious to damage unless attacked with a stick of TNT.
For what it's worth, I've experienced identical problems using my Gamefest Redneck Collection copies of the game but did not have any issues with Redneck Rampage itself. I've yet to get around to playing Redneck Rampage Rides Again. While playing the Gamefest collection, I've been using the 7 September 2008 build of DOSbox with my own custom configuration and for the GOG release I've been running with the stock settings.
I've gone ahead and uploaded a save at the beginning of the Bigfoot Convention level here.
Any help would be just absolutely super. So close to the end and the expansion is otherwise totally up to snuff with Sunstorm's other Build engine expansions :(

I just finished the whole Rednecks Rampage Collection and I have encountered the same problem.
Both original Redneck Rampage and Redneck Rides Again run just fine with no graphical or gameplay issues, but the second chapter of the Suckin` Grits on Route 66 expansion is full of flickering semi-transparent textures and alien Vixens who do not attack you and float through the air.
What`s worse, the final level in the second chapter of this expansion cannot be finished without cheating (for keys) or pressing on a random location on a certain wall in the Oddity Museum, which opens a door that leads to the final key. The reason for this is that the alien symbols that should be shown and pressed in a specific spot on the said wall are somehow missing.
It seems to me that the CON file or files for the last few levels of Suckin` Grits on Route 66 are bugged. The problem could very likely be solved if the CON files would be overwritten with the files from an older release of the Route 66 expansion.
GOG team should look into the matter and try to replace the corrupt files.

It's not a matter of CON files at all.
Those are missing textures, which reside in the .ART files. Sucking Grits on Route '66 uses new textures, which apparently aren't provided with the game.
Usually BUILD addons have new texture files which overwrite the original ones. I can't see any new .ART files or .GRP files (which can contain the .ART files themselves. only REDNECK.GRP which has the original Redneck Rampage data) so I guess we'll have to leave this to the GOG team.
EDIT: Checked the game out, since at least most of the textures work (like the new alligators and signs), it must miss like just one or two new textures.

It`s been ten years since I toyed with Build engine so I forgot where certain game data is stored.
I agree with the missing .ART files, but there must be something more, since flying and docile Vixens are not in any way linked with missing images.
A while ago I have read a topic, where someone had the very same problem with Gamefest version of Redneck Rampage Collection, but luckily he also owned the older original version of these games. He claims that he copied all the files from older releases over the newer version and the game then worked without any problems.
Bear in mind that this is unverified information and someone with both GOG and older versions of Redneck games should test this and post here how it went.
It˙s a shame that these glitches are present in the GOG release, because I have very much enjoyed the Redneck Rampage series, but the last part left me with bitter aftertaste.

I never owned the retail version of Route '66 so I don't know how they pulled it of, but I'm assuming it had completely new ART files.
But the case of only few missing textures in-between sounds like the new textures were manually added one-by-one into the ART files, it's the only thing that would explain one or two missing textures imo.

I played RR and RRRA a looooong time ago. Always remembered these games very fondly. I'm not entirely sure, but I think I must have played pirated versions because I never had any money.
Fast forward many many many years.
I found RR, RRRA, and SGOR66 in the bargain bin of CompUSA or some store like that. This was about 3 or 4 years ago. I eagerly purchased the games but found that I couldn't play them. Not even with Ken SIlverman's VGA patch.
I tried again about a year later with DOSEmu. Under Windows sound wouldn't work. Under Linux I amazingly enough got sound, but the game was way too slow.
About a month ago I tried again with DOSBox. Lo and behold they worked. Finished RR in about a week and loved every second of it. Finished RRRA and loved every second of it. I'm now playing SGOR66.
When I was on the Crystal Lake level, 2 days ago, I noticed some hall of mirror effects (missing textures). It was on a sign or two plus a wall texture near the end.
I'm now on the next level, Bigfoot Convention, and the HOM effect is everywhere. I did a Google search on "sucking grits on route 66 missing textures" and this gog site was the 2nd return result.
I'm not sure what gog is. I read "about gog" and I'm still kind of wondering. Are you guys who purchase the rights to distribute old games? How do you get the money to purchase the rights?
Anyway, I can confirm that I indeed am playing the retail version of SGOR66 (store bought - not pirated, and not from gog) and I see exactly the same things.
1. The missing textures are precisely as you describe. There appears to be a missing sign texture, and two or more missing wall textures. The only patch for the game I can find is related to the game not running on pentium 2 machines. I can't find anything about missing textures.
2. The vixen problem is strange. First of all, I'm not 100% convinced that it is a problem; perhaps that's just the way it's supposed to be? However, I did make an interesting observation that wasn't mentioned here. The behavior of the vixen matches EXACTLY the behavior of the alligators (except the upward downward movement). She does the same amount of damage when you're right next to her. She has the same stochastic north/south/east/west movements. She even makes the same hissing sound that the alligators make. Same level of aggression - she'll mostly ignore you unless you're very close.
In fact, now that I think of it, there was a part in Crystal Lake where you're actually in a lake with a bunch of Billy Rays and Old Coots on the shore. There are a whole bunch of vixens in and around the lake, which is kind of like what you'd expect the alligators to be doing.
Interesting that there seems to be no mention of this anywhere.
I'm no longer a grad student, so I don't have the time to investigate, but if someone did, I wonder if you could discover something by using the BUILD level designer to see what texture ought to be used there...

The Bigfoot Convention is indeed the level that suffers the most from HOM effect. It is actually so bad that half the time you are bumping into these flickering textures, unable to move. It gets a bit better after that, but in the final level it gets worse again.
Now that you mention it, I seem to recall that the "bugged" vixens were making some hissing sound just like the alligators and that they were mostly floating around the cave and water areas. I guess some textures got mixed up.
Someone with some BUILD engine skills should look into this.
I have alerted the GOG support team to this problem. I hope they will manage to solve it.

I think I found the problem.
Will have to do some more investigation on how to easy fix it.
Might provide a workaround for people who troubled by it though.

I just beat the Suckin' Grits expansion and noticed none of the bugs mentioned here. Textures were fine and alligators were alligators. :) I bought this game a couple of weeks ago. Perhaps the installation package has been fixed and you guys should download it again?

I downloaded the game again and the issue has now been fixed, so the original poster should mark the topic as solved.
Thanks GOG!

ah yes. they included the fix.

Hey, GOG team! A suggestion: if you apply fixes to your games, it might be nice to send out a little notification to customers.

So, what was the fix?