That's a preatty neat base! Looks cool to me. But you are limited to desert-like maps.
The thing on making mountain is, for me, the "roundity" and naturality. I mean just imagine the form of a mountain in real life, they are not that straight right?
What I always do is just draw the mountain with any tile and then connect each tile with his appropiate part of the mountain? Get it? Maybe I don't know enough english to express this but I'm trying my best xD
Anyway, that map looks nintendo-ish, and it's not bad at all!