I think it was the overall color scheme more than anything, but the circular motifs - the grid and those colored rings - just gave it a nice sense of balance that I liked. I tried to do my own version a couple of times, but the thing that always made me grind to a halt was mountain and river placement. I couldn't come up with a way to place them (mountains especially) that didn't look horrible with the rest of the design. That's why I was waiting for you to work on yours some more, so I could shamelessly copy whatever idea(s) you settle on for the mountains.