It's coming along..

What I do for sparse vegetation (photoshop) is use one of the spatter brushes, usually the 59, and resize as needed to drop in vegetation a single click at a time. I'm using layer effects for the most part, along with the pattern stamper (a la pasis) so it tends to work out pretty well.

For the mountians, you could give them some more valleys so they don't look 50 miles in altitude

But it looks like a good layout and shape to me.