If you're so lazy that you don't even feel like changing your desktop wallpaper then this program is for you. WallUp takes care of the hard task of renewing the wallpaper according to the frequency you set in the program's configuration options.
WallUp has a simple design and also works in a very simple way. It enables you to create separate albums, each one with its own pictures, so that you have a really wide choice of wallpapers. Unlike other similar applications, it seems that WallUp can't be minimized to the system tray so I don't really know if it should be left open or closed anyway.
I also felt disappointed when trying to test the custom screensaver feature explained by the author on his website: I couldn't find it anywhere and the Help section wasn't useful either.