I like your colours.
As for mountains, I usually experiment with brush settings (with the chalk brushes mostly), and creating a layer with bevel&emboss settings. I always try to pick a green/brown colour for the hills, a brown/grey colour for the mountains and a white colour for the tops, and I make them in seperate layers. Each layer gets a layer style (bevel & emboss), with settings on 'emboss' and 'soft chisel', and a texture (just browse for a 'stony' texture, you can find some links on the forum as well). At that point, it's just playing around with the settings 'till it looks good.
I know this isn't too specific, because I never do the same thing twice, but I hope it helps some. There are some great tutorials on the forum as well, you could try to find something there as well.