there was a chinese site we found ages ago, that had about 100 skins. But then we found out he was a member of this site as well, so we asked him if we could add all of his skins to our site as well (as not many english speakers understand chinese) and he said yes. So now we have his entire collection on this site...
Other than that, i don;t know of any other sites.. Why ? ran out of good skins to take from us now There is always one other answer... make your own.. that way you can have any skin you want..
yep, hell of a lot of resources. even simply things like a brick wall. you can either waste valuable thousands of polygons to model a brick wall, with all of its little bumps and chips and things.. or you can just use a Bump/Normal map and have 1 flat polygon and let the textures fake the look of bumps. It doesnt actually add any bumps to the flat wall, all it does is make the light shine in certain ways which give the effect of bumps.. If you go up to said wall really close and look along it (not face on) then you will see it is totally flat.
They are really nothing fancy, basically the same as a black n white bump map, and they have been around and used in games since forever.. well since Nvidia got involved with doing gfx at least.. Every since games switched from using sprites to using 3d geometry they have been using bump/normal maps to fake depth/detail.