I have heard of a 640x480 patch, but have no personal experience with it.
Keep in mind that this is a completely software rendered game. At its highest resolution (512*384) it brought machines of its day to their knees. If you were to raise that to 1024x768 -- twice as large each way, four times as many pixels -- you would need four times as much processing power.
Of course, we've GOT four times as much processing power now, so it would really be nice to see it in high res glory...
EDIT:
Trying to locate said patch, I ran across this:
http://and.intercon.ru/index.php?id=releases (search page for Outcast Lives Forever)
It's just a map viewer, not a game, but should be pretty (I'm on my netbook and haven't tried it yet, so I can't make any recommendations or warnings or any other kind of statement)
OK, finally tracked this down:
<quote source=
http://www.rage3d.com/board/archive/index.php?t-33865846.html>
The only way to get the patch that increases resolution working is running the game in Win98, since the resolution patch doesn't work in 2K/XP.
This resolution patch can play in WinXP normally. (may be with compatility mode or something i can't clearly remember) + Update Patch
http://outcastii.free.fr/FTP/loaderp_eng.zip Outcast loader + (159 KB) - Now you can play to Outcast in 640x480. VB6 runtime is needed : vbrun60.exe. << DEAD LInk for VB6
http://www.outcastii.net/
Great Fansite.
</quote>
AAAND one last link to a forum that has various links:
http://www.openoutcast.org/board/viewtopic.php?f=16&t=756&p=6431&sid=445108be321401e5438b94676d2c967e And at least one place to get the 640x480 patch, which unfortunately won't work in 2000/XP/Vista/7 :(
http://www.simeon-carstens.com/ (you may need to translate it from German)
(Actually, it apparently works even on Win7 64bit (for some people) if you set all the EXEs to Win98 compatibility mode and then use the normal launcher -- but it also apparently crashes a lot)
OK, wore myself out there. Will post later if I actually get anything working at higher res :)