Just thought that we could use a wishlist for additional materials. If you know of some things that could be added to the games available on GOG, just write about it here.
I bought Stonekeep today and learned through Stonekeep forum that there was a story added to the game when it first came out. It was called Thera's Awakening and the action took place just before the story of the game. I hope GOG can get the story and add it as an additional Stonekeep material.
What other materials do you know of and would like to see on GOG?
EDIT: Spelling.

I'd like to see Redneck Rampage come with an ini that enables mouse look (configuring it is fine, but it'd be better if we didn't have to). I'd also like to see UTGOTY have the enhanced textures, come as an additional pack that only requires you to run an installer, as opposed to copying files, editing the registry, and copying files again.

I'd like an attractive nude lady with each purchase. I know I'd buy a lot more games...
On a slightly more realistic note, I'd be interested in some original material if possible. A current retrospective on the game written by the devs (assuming they're alive, contactable and would agree) or some design documents would be awesome if it could be arranged.
Game trailers & commercials (both print & tv) would be good if that wouldn't cost any more to get, I've always been interested in how things like games are advertised, often through lying and directly claiming or strongly implying that cutscene or video footage is actual gameplay...
I know it's mostly a recent thing but those special edition extras you get like "The art of <GAME_NAME>" would be a nice addition too. Also if you were selling Elite, I'd be disappointed if I didn't get the novella.

I'm already impressed with the capacity of gathering stuff for my favorite games here. Yes, that wishlist could be nice, but it'd probably only lead to impossible stuff.
Could be a nice touch, who knows? Joystick (an old british abandonware site) had something similar.

Does Redneck Rampage come with the Cuss Pack on GOG? If not, then I want that.

It's additional, as in, not in the installer, but you can download it extra.

You thought about including a nude lady as well? Awesome, I look forward to that!
Well assuming she's cute of course

I'd like to see a different one each time, and preferably, non-professional models, as amateurs are much more entertaining.

I'd just like to see more materials that are unique to each game. Mostly, extras include a manual, some wallpapers, some avatars and sometimes a soundtrack. While these things are all fine, I'm hoping for more extras that were included with the game originally, like the comic book from Beneath A Steel Sky, things like that.

I will take a Japanese redhead as my "additional content"....

Various posters: "I want boobs with my games!"
Well ain't that totally geeky.. ;P

I second this. Unreal music is brilliant.

I also want that, I also would like to see more wallpapers and avatars.