Change wallpaper upon startup with auto fit options, using Wallpaper Shifter

Wallpaper Shifter is a little freeware utility that starts when you login to Windows, picks a random wallpaper from a list and then it closes.

Depending on the wallpaper’s width and height, it can automagically scale it to fit your desktop without deforming it’s proportions.

It can also delete the current background from the disk.

I found Wallpaper Shifter fast and easy to use.