Suggestion: A map-free map
The central part of most maps is, not suprisingly, the mappy bit, but they also contain cartouches, borders, scale bars, legends, title frames, coats of arms/flags etc. This idea is simple: make a map that leaves out the mappy bit. The winner will be judged on the other components of their 'map.'
This idea might work best if each entry simply leaves a large empty hole in their image, or perhaps everyone has to use the same standard map (although that could limit contestants in style/genre a it).
What do people think?