Thank you very much for your feedback!

For the mountains I used a crude handdrawn map with the most important mountains, then I created heigthlines using those information, and finally I used the smudge tool and some blurr to smooth it out and create ridges.

I think I will have to experiment a bit with the bumpiness and sharpen the peaks.

Concerning the fade between mountains and grass, you gave me the idea to add some hills around it (would also be logical) I'll see when I get to it, thank you very much!

The border colors are chosen because of the individual flag-colors of the countries, but I guess I should just chose some that look good. The top-left country uses grey and green in its banner.

The colors on the map are 90% from RobA's great Gimp Tutorial, so I cant take credit here