Hi,
Great web site, the design is easy on the eyes (like 2C mentioned). Your navigation is clear and has options you'd expect to assist you in finding the right wallpaper. You may however want to add a "Categories" navigation item and have a page dedicated to listing all the categories. Love the statistics box, if I was visiting a wallpaper web site knowing others are looking at it too will definitely keep me there longer.
Below the thumbnails, the names are cut off. I suggest spacing them out a little more so the full name can be displayed.
The colors on your logo don't go well with the rest of the design, I suggest a strong colour on your orange background like a white.
The models names are in the links, which is good for SEO.
http://www.hotcelebritiespictures.com/view/Shakira-11/6271 But try to keep your links consistent, you also have links with underscores instead of dashes
http://www.hotcelebritiespictures.com/celebs/Charlie_ONeale/25 (I personally suggest using dashes as underscores can be harder to see)
Good luck.
Richard