I played the demo version of Slave Zero back in the day, and one of the things I enjoyed was the anime/Evangelion billboard images. When I finally got the full version, I was quite surprised to find that those textures had been replaced!
Thanks to this forum post, I went digging through the demo and full version .tex files. There are a number of minor changes: Some scaffold textures are darker or have an added light. The Klieg, Otto, and Vitriol billboards where either made brighter or dirtied up. s_sign_dragon_B is the "Tristan" sign and has the words "Amber Ale" at the bottom. s_sky_mission15.tex has a red clouds on the bottom, rather than being all black. The loading screen is different, showing Slave Zero standing still rather than shooting. The menu font is different, being textured and harder to read. s_signage_girl has a vignette added.

The completely swapped textures are the ones in the attached image. Clearly there were some copyright and adult content issues in a few!

If anyone would like to add those textures from the demo into their full game, I posted them here:
forum.xentax.com/viewtopic.php?t=19293#p164560
You have to be a registered member to download, but registration is free.