Here's what you can with those trees in photoshop in just a few minutes:
1. Create a new layer and use your brush to plop em down in a white color.
2. Hold down the ctrl key and create a new layer at the same time by clicking on that icon (this will create a new layer underneath of your trees).
3. Fill this layer with black.
4. Click on the trees layer and merge down (ctrl+e).
5. Filter - brush strokes - spatter.
6. Select -color range = black
7. Hit the delete key and then deselect. Your trees now have roughed up edges.
8. Apply your styles, colors, patterns, filters, etc.
Overall, a nice lil map and you have a lot of potential.