I've finally started replacing textures! My friend who I mentioned earlier was too busy with college stuff to work on textures, but as a high school senior who manages the few assignments I get very well, I have copious amounts of spare time!

The textures are based on the ones from standard.wad in design, but have a cleaner look matching the somewhat cartoony visual style of the characters.

I played through the first level with the new textures in the latest video:
http://www.youtube.com/watch?v=9PGXqu4jsY0

Thanks for all your comments!