Not sure if this is the proper place to throw this idea around, but a REALLY cool feature for this program (to me) would be to set a sort of timeout lock for images from wallpaperfusion or where ever.
For some reason I tend to see a lot of the same backgrounds several times a week/month. Whatever the interval, I know there are 1000s of wallpapers out there that could be downloaded and used on my system, thus eliminating duplicates. I just feel like I see the same images all the time no matter what I do to avoid them (adjusting my search, my source, or other settings).
A neat feature to cure this would be a sort of timeout for images that won't show up in the pool of random images for at least (whatever length of time you want). Or choose to eliminate them entirely.
Either way, I love this program and I'm just voicing a thought that would be kinda cool.