Thanks to michaels for the comments on Wallpaper Changer. He mentions an out of memory exception when browsing the previews with more than 50 images. On my machine, I've got 68 wallpapers, and I've never seen an OOM exception, so I'm not sure what's happening there. Perhaps your wallpapers are bigger than mine? Mine around about 1MB JPEGs (on average) usually about 2560x1600.
Anyway, michaels, you didn't leave any contact info, so if you want to mail me (wallpaperchanger (a) codeka.com) with your details, I can try to figure out what's going on. In the meantime I uploaded a new version which uses a slightly different method for generating the preview. If you're still getting OOM errors, then please drop me a line at the address I just mentioned and I'll see what I can do.