My newest creation, Wallpaper Director, is available on my website.
Wallpaper Director is an easy to use application for Windows based computers with which one can easily have a different wallpaper every day or even every time the system boots. Wallpaper Director does everything automatically once the user selected the images he would like to see as desktop wallpapers. Wallpaper Director is able to resize the loaded images to fit the screen resolution of the actual desktop maintaining the aspect ratio of the original image. Once everything is set there is no need for user interaction for Wallpaper Director to work.
* Automatically change the wallpaper every day or every time the system boots
* Handle unlimited number of images
* Fully automatic operation
* Automatic resizing of the image keeping its aspect ratio
* Use of filling color
* Multi-language support
* Technical support
* Built-in Help
You can download it from its website:
Wallpaper Director Website

I use WinXP so I have no idea if it works on Vista or Win7, but I think it should. Anyway please let me know. I was able to test it with the regular 4:3 screen and 16:10 screen but please let me know if there is any problem when resizing the image.
It has multi language support, the language files are in the subdirectory called 'languages' in regular txt format.
Neuronic