There are three things that I see wrong.
1. The upper-right island doesn't have any routes/cities; you should add some.
2.The island itself doesn't look like much of a island, it's about five times bigger than Hoenn

;;You can't change that much, though. So on your next map, you should save a map of Hoenn, and put it beside the first starting outline, so you can compare sizes.
3. The separate shades of green are too sharp, you don't need to change this, I'm just being nitpicky. If you want to though, try editing the edges so that they look smoother.
Good map for first try! I've seen other people do way worse, beleive me. *cough*brother*cough*