Ok please don't take this the wrong way but i believe that there are some things you must change to get a popular site!
your site is nice in speed but your design/colors are killing your site!
what i recommend is:
change the background color to either black or what!
use color's like bright green and some silver!
make your wallpaper sizes be a drop down box for selection!
i have made a preview image below to show you the type of thing you should think about as the colors you have chosen are very calm and a wallpaper website needs to be a bit exciting!
note: i am not telling you that you must do your site like this! but i am recommending to change from the old colors to some of these!
with a little bit of designing and some time your site will look great!
sorry the img is not great i only did it quickly you are welcome to use anything on there and if you want the psd for it i can send it to you!
please dont think i am being rude i just believe that you site is great if you change it a little bit!
hope it all goes well