The best way to integrate (blend) mountains

[- Max -]

If you're not going with more texture, you'll have to fade the grey tone of the mountains with green by gradually erase it smoothly at the mountains base (and you can do it a bit onthe outlines aswell) or overpainting it. Aldo use some mountains color closer to the background color may help.

[Doobyfrucan]

These are in a different style to the mountains you are using, but you may find this tutorial link of interest: http://www.cartographersguild.com/tu...ks=#post173184

Kudos to Tortan for that and other useful tuts.