This isn't so much an AF.com suggestion as it is an AW.com suggestion. Despite the widespread use of widescreen computers, I notice that a lot of wall-makers are using the same old resolutions: 800x600, 1024x768, etc etc. I know that wallpapers are the creation of the artist, who have complete creative control over details such as size, but this unfortunately causes an issue. Users of widescreen resolution, like me, are left to dig through pages and pages of walls in order to find one that fits. So, I have a suggestion.
Why not add a search feature to AW.com that allows for size search. This could be as simple as two categories: dimensions deemed "standard" and those deemed "widescreen". Or you could go more complex and add a search feature for every size uploaded (for example a list of walls that are 800x600 or 1280x800 or 1920x1200). Or you could do a combination of the two.
I think this would make finding a suitable wallpaper easier. Also, it will encourage users to use walls from anime they may not have seen before, or never heard of. I'm always on the lookout for interesting walls, it doesn't always have to be from a series that I'm familiar with.
I apologize if something like this is already in place and I just missed it. Or, if this is in the wrong forum. Didn't think it went in the AW forum, but it might.