I came across a very simple way to make your own fantasy maps (Thanks to LaurelQuade).
All you need is a picture of a cloud and Photoshop (CS4 in this case).
1. Open your Cloud image in PS
2. Select the Magic Wand Tool
3. Right Click your image > Click “Select Inverse” (This will select your cloud)
4. Click Image > Adjustments > Threshold
5. Move the Threshold slider so that the cloud is completely white
6. Hit OK when satisfied
7. Click Edit > Stroke
8. Change Width to 2 or 3 px (This will outline your cloud)
9. Change Color to black
10. Click OK
11. Change your Primary color selection to Green
12. Using your Fill tool, click inside the white areas to make them green
And that’s it. You now have a map to work with!