Okay, I've seen it on a youtube vid, but the easter egg described at [url=]http://www.tomshardware.com/forum/19899-13-realmyst-easter[/url] seems to be missing. I get a white static screen. Is this an error on my computer, or was it removed from the GOG version?

Unfortunately i didn't kept my saved games after finishing RealMyst the last time i played it, so i can't check that one for myself right now, but i don't see how/why anything would've been removed from gog's version.
Anyway, here's a page covering most if not all of RealMyst easter eggs. Some spoilers in there, obviously.
Also, Huevo and Vika in more detail [url=http://home.comcast.net/~zardoz99/RealMyst/huevo_and_vika_cracked.htm]here[/url] if you want to check it out.
Edit:
eh ,eh, i had totally forgot that you can go straight to Rime after a quick stop by K'veer so no need for savegames ;)
I didn't played with the crystals long enough, but there is in fact something there, although i'm not quite sure what it is.
Edit2:
Ok, i just figured out what it is and why i wasn't remembering it as an easter egg. It's not an easter egg at all ;)
That bit is explained in Atrus' Rime Journal, except on his journal you can't make out the last crystal cause it's smudged, so you have to get that last crystal shape by trial and error. Basically you can do the same thing Atrus' did while we was experimenting with the imager and crystals when he was on Rime with Sirrus. And the Age in question is just 'an Age', nothing more specific than that.
I uploaded a video to you tube where you can see the whole thing. It's here.
This is with gog's version btw, so nothing is missing ;)

Well, I've seen it on youtube before, but I still don't understand why mine isn't working. It displays white static, not the star fissure, so I know I have the combo right
EDIT: Unlike on yours, where it randomly flickers before you see it, mine jumps straight to the white.

I don't know why it's not working for you either but at least know you know it's not an easter egg ;)
If you're getting everything from the imager except this, that is weird, and i honestly have no idea about what could be causing it.

One of the file related to the easter eggs (vika.avi) is corrupted in the GOG version. That's why it doesn't work.

Why do you say it's corrupted ? Cause WMP is probably telling you it can't open it when you double click on it?
I'm pretty sure i've mentioned this already, i'm running gog's version and i have no problem getting the sequence in question from the imager. The video i uploaded to YouTube was done with gog's version. So even if vika.avi was corrupted, it clearly couldn't have nothing to do with the sequence in question, otherwise i wouldn't be able to get it either.
Grab Riveal and extract the content of the game files. You'll find that vika.avi contains 7 stills, and none of them are even remotely related to what you see in the sequence in question.
Or just use the [url=http://home.comcast.net/~zardoz99/RealMyst/huevo_and_vika_cracked.htm]link i posted above[/url] to see the contents of vika.avi. The only screen missing on that link is the .bmp used for the 'static' .

No. It's because the mask file that I made to decrypt the stills doesn't work with the last one.
I guess I should have read the thread completely. So, that egg may work but the huevo/vika doesn't work because the vika.avi file is corrupted.

You're right, even if it's completely unrelated to the 'egg' mentioned by the OP, the vika.avi is faulty indeed. I can get the first image from vika in the imager, but cycling through the colors on crystal #1 doesn't cycle vika's stills.
I uploaded the vika.avi file from my retail copy of realMyst to media fire, link, and with this one i got all of vika's stills, so give it a try if you wish.
Huevo is working, even because it pulls the stills from huevo.avi, not vika.avi
And the 'egg' mentioned by the OP, the one described in Atrus' Rime journal is also working.

In my boxed version of realMYST I also had an issue in that I couldn't see the mystery age "egg". It turns out it was some wierd issue with my graphics card, and it worked on another computer. so be aware that it seems to have issues too depending on the graphics card.
By the way, theRealXCV, are you the same RealXCV from the Myst Community Forums?

Yes.

Uninstalled a while ago, and thinking about reinstalling; will try again then.