I have both UT GOTY and UT 2k4 from Steam. Unfortunately, they don't come with the bonus wallpapers and stuff that the GoG versions come with :(

Can someone upload the extra material for me?

I'm assuming that my request if perfectly legal since I own the games and the extras are supposed to be free. In case I'm wrong, mods can delete this thread.

I doubt it, besides there is no way to really prove that you own it on steam is there?

Just buy it a second time on gog as well besides gog is far more pure awesomeness then steam. That saying I haven't board UT99 and Unreal here when I own both of them on my shelf.