I'm not sure Isometric mountains are the ideal solution for what you've got going in this map. It looks like a bit of a clashing style. I'd consider mountain types like what HandsomeRob does in his maps... not sure of how those are accomplished, though.

Also, with the green and forested sections of the map looking so nicely textured, your desert and grassland look very flat by comparison. You might want to try applying some textures here, if you weren't planning that already.