I think people should just visit that website (N900wallpapers.com) and select the wallpaper(s) they want to use... IMO, anything else is just a waste of time and space... I mean, I don't think people changes wallpaper every day and want to have hundreds of them on their device... at least, I wouldn't do that.
In the mood of changing images? a check on the website, and I'm done
themes require an installation instead, so it's a different matter. wallpapers just need a download and "set as wallpaper" selection..

I agree though on a serie of wallpaper packs from time to time, of, lets say, 1000 wallpapers each (hosted somewhere else for bandwidth?), for those which want them all locally without too much work.

just my opinion.