The most interesting methods I've seen to prevent image downloading is to slick up the image into multiple parts and put them together using HTML. That means,

The most interesting methods I've seen to prevent image downloading is to slick up the image into multiple parts and put them together using HTML. That means, you have 10+ parts to each image. If you want to download it, you'll have to grab each part individually and put them together in an image program. That, or you can just take a screen shot but you'll lose out on some resolution.