It turns out that these two sites work really well - and easily well - for photographs too. These sites make high-quality prints, so you'll want to be sure you upload fairly large files with high dots per inch (DPI). Nothing less than 300 and 450 to 600 is probably best. Upload .png files if you can. For larger prints, a jpeg just isn't going to produce the quality you need. There are plenty of good programs for manipulating your image for best quality but, if nothing else, I'd recommend the program IrFanView. It's free and has a lot of different functions to help.
Another easy-to-use program for increasing quality I use really often is Free DCE. If you haven't heard of it before, this magical little program does an amazing job of taking a so-so photo and boosts it to print quality with just a few adjustments and a click. Download and use it - you'll be very happy you did.
At any rate, two of the sites I love posting my artwork to are Fine Art America which is building and transitioning to Pixels.com and, more recently, Art Pal. These two sites let you set up your own gallery - all free of charge - with nicely designed popups for each image, and provide you pretty decent traffic to sell your images. Art Pal also allows you to boost your placement in the main gallery listing for fifty cents, which will instantly show your image in first place of all other images on the site. Speaking from experience, it won't stay there long, but it doesn't slip down the rankings very quickly, so you could have your image at least among the first 100 images for anywhere from 2 to 4 hours and sometimes as long as a full day or two. That's a lot of great exposure for less than a dollar.
In the video embedded below, Brad Scott Photography over at YouTube has a brief walk-through of Fine Art America to show you how that works. You should get a pretty good idea of the selling potential for your photos. Art Pal works pretty similarly. Give it a watch.
Owner, Art Director