I use a Wintel PC system and occasionaly make desktop wallpapers from my jpegs. I re-save the jpeg as a bitmap image and then put it in the windows directory.
In the past I've found that trying to put a jpeg as wallpaper on your desktop can be a quirky proposition (like having to make your desktop an "active desktop" which I don't like). This is why I use the bitmap format for wallpapers.
If I want to make wallpapers for people on a MAC platform, can they use a bitmap image? Or do I need to save the file in another format? If so, which format would be the "proper" one to use for the stated purpose?