I dunno how legitimate this logic is, but I don't think desert forms next to mountains very often since mountains are perfect runoff points for rainfall. Unless it's just a very dry region, which wouldn't really fit with the nice big lake area just east of it and the forest across the way.

If you're aiming for a sort of Mediterranean area, I'd say there shouldn't be any fir/pine/northern vegetation at all. In fact surely there shouldn't really be any forests - I don't know much about the med, but it's always palm trees to me that said, you have a lot of forest on the map - I'd suggest you break up the forest on the southern/eastern continent a bit more, since it is pretty much a solid big forest as it is right now.

Remember that maps don't show every tree, just actual "forests". You can have tree-y areas without it being a forest.

As for the commission, typically you'll pay a full payment to secure copyright and publishing rights when you first put the commission up rather than pay extra later to be allowed to publish it.