I can see the 5 wallpapers.
I don't have previews, but I can open them...
Strange(r) problem
PS : download PicaView, it's a cool software with which you can have previews by a simple right-clic, convert your files, etc. (it's not a freeware)
edit : I've just noticed that it's a PSD format. That's why you can't see them. The 1st wallpaper is a JPEG.