I can engrave most images and logos (even some photographs) into the brass sides of the Zippo and I can do one or both sides. The diamond tip I use scratches through the paint and exposes the brass underneath and it really stands out in a cool and unique way.
If you don't have an idea in mind, some of my designs from my knives look really nice on there too, such as the Battle Torn Flag, We the People, etc.
You can email or an image or idea and I'll most likely be able to engrave it, of course images with sharp contrast and edges tend to work best.
Prices are $40 for a matte black Zippo with both sides done, or $35 for one side done.