I'm a little confused, are you looking for sites that have tutorials on how to render pics or are you looking for sites which provide fully rendered pics?
Because;
1 - I can teach you how to render pics. (It IS a pain, but it's better than searching everywhere for a pre-rendered pic.)
2 -
http://www.gimptalk.com/forum/topic/Renders-452-1.htmlThat site has a whole list of sites for renders, though like half the list, I believe has died off.
Oh and this belongs more in the Musings of the Pencil. I'll sticky it for easy access for others for renders.
I used to use Planetrenders, but now I mostly just do my own rendering.