I think this is a really good idea. How about a smaller charge, say, $0.50 an image, or tiered, at $1.00 for the first image, $0.75 for the next, $0.50 for each after?

Perhaps a discount on the next sale if a previous sale was successful?

I know my idea isn't perfect. However I think Zed should think of something along those lines. One dollar flat per image might discourage bulk sales or products that need visual defining.