Landscape Shading in GIMP?

[Ethel]

With the help of a few wonderful tutorials I recently managed to draw up some maps for the current D&D campaign me and some friends are playing. I decided to try also drawing battle maps with some of the tricks, but I ran into a big of a snag. I can't seem to figure out a way to get shadows/lighting to look good for landscape features like hills/cliffs/etc. Does anyone have any tips (or a good tutorial on that subject?) (I am using GIMP.)

[Redrobes]

Its easier with a height map and a 3D app to auto generate it for you but in absence of that I think its better to do the shading / lighting on a white image of the same size and use filter multiply for the result with the colour image than to try and modify the colour image itself.

[Ethel]

Ah okay, I'll try that out. Thank you