This was my second book cover assignment, as far as I can recall.
For the selected option (above), I used a muted pastel palette, and the dotted outline of a rhombus-esque shape made by joining the Western, Northern, Eastern and Southernmost points of our country, marked with their corresponding latitudes and longitudes. The dotted horizontal line, of course, is the Tropic of Cancer. I thought the dropped pin might make it a little more contemporary.
The cover option below is one of the others that were not chosen. While it had earthier rust tones, I suspect it may have been severely disadvantaged by the occurrence of an actual map.