A website that has been a favorite for years is InterfaceLIFT. My computer desktop changes every five minutes (not an exaggeration-- it's a setting), and several of the images are from this site.
User-submitted images are posted in "The Loupe," where other users can vote for them. These images are available for voting for two weeks. If they get enough votes, they will be posted on the main site.
I currently have five images in review. Please vote for them!
Have a Cookie
Deep Firebrick Red
Yes, I took each of those photos. And yes, I made the cookie. It was delicious.