Metius - The Grand Basin

[Momiji]

The concept for this worlds design is simple, the world is set inside a giant basin (Or to those of us sitting on the outside looking in, a giant crater). This is the world of Metius.

There is a very detailed and vast history to this world, that I won't go into, simply because I've so far written a small book on the subject... Feel free to ask questions.

My biggest problems when making this map, is that of the forests, most of the basin is covered in these lush forests that a lot of the techniques I found on these forums didn't quite look right when used. Also, showing that the top right of the basin is a desert still doesn't quite go right.

I'm also at an almost loss on how to do the key for the map, my previous attempts have left me hanging and as such, would appreciate any pointers for that.

Anyway, I would really appreciate comments and criticism.

EDIT (Note): The scale of the map is 1 block = 20 miles (the blocks around the border that is) The basin is around 350 miles radius at its greatest point.