Thanks Freodin, I think part of the river problem is that they may be a bit too 'thick', but it'll do for now!

As for the mountains:
I started with a clouds layer, then manually brushed lighter and darker areas where I wanted the mountains to definitely appear.
I then took a second clouds layer and blurred & merged them together so my hand lightening became more random & less obvious again.
Then one spotlight lighting effect and four corner omni lights effect.
Then colour overlay grey-brown and inner bevel, soft chisel 1pt to bring out the bumpy relief appearance.