At first I felt like the maps of Tuniitaq and Aztatlan were too plain, too austere, but I really couldn't put my finger on what would make them better. I thought about adding mountains, but I knew that wasn't quite it. Not by themselves, anyway. Suddenly, inspiration struck (as it often does) when I least expected it: while re-reading Robert Jordan's The Eye of the World, I glanced at the first pages of the book and realized that the map of Randland (or whatever it's called - Jordan never really gave a name to the world he spent decades chronicling, strangely) contained exactly what I was looking to add to my maps! All the forests and rivers and mountains, all the squiggly little waves along the shorelines, all the little details which set hand-drawn maps apart from super-accurate and super-sterile Google Maps screenshots... those maps were exactly what I wanted my maps to look like!
It just goes to show that when you can't figure out what to do next, the best answer is often "take a break and go do something completely different".