This map looks very nice! However, as you mentioned it is very basic. I would definitely give some darker colors so they’re easier on the eyes, make it more explorative, add more areas, make the buildings different. This would very likely hurt your budget because of the buildings i suggested but if not that, change the colors of the buildings up a bit (e.g. take one building and add some banners, each building would be the same but different banner colours or icons), add like a statue in the center. Use rocks, bushes, possibly even more types of trees.
Good luck on your game though, hopefully i helped.