Adding details to a world mao

[hephalumph]

I've created the basic layout of continents for this world. I have in mind some of the geography I want included. But I don't have a complete vision, and I can't seem to get what I have in mind, done in a manner that is either aesthetically pleasing or natural looking. I've tried various tutorials for mapmaking, I've used premade terrain brushes in photoshop, I've even tried copying elements from existing maps and editing/pasting them in. Nothing I have done has worked - not to a point I am satisfied with it.

Attached is what I have (I can post some of the failed attempts at adding details, if desired).

There are three main continents.

The central mass includes a smaller continent-sized island which used to be connected by a landbridge (hopefully evident where/how) in the past. Otherwise it has no islands considered a part of it. It has the largest mix of terrain and climate. There are three mountain ranges, one coming from the landbridge, one coming from the southwest peninsula, and one coming from the northeast peninsula, all converging at a massive crater/valley in the (more or less) center of the main continental mass. The southeast will be arid/desert, the central crater will be a natural deciduous forest that has mostly been cleared by man, with plains and swamps and a fertile river delta to the north/northwest. The large island will have a bit of the mountain range from the mainland continuing into it, otherwise it will primarily be rolling hills and plainlands, with a large river splitting into two smaller rivers, and dividing it into three fairly equal sized areas. Politically, this continent (including the massive island) will be split into 14 regions; the central crater being one, and 13 other "countries" spread throughout the rest. I have no hard plans for these political borders yet - I'd hoped to have natural terrain provide the clues (mountains/rivers as borders). But since I can't make good looking terrain, I'm stuck there as well.

The northeastern continent and its islands are a mixture of rolling hills and plains, with a decent amount of wooded terrain. No real mountains or swamps, though a few rivers and lakes are probable. Politically, this is all one massive country/continent.

The southwestern continent and its islands are lush tropical and volcanic - much like the Hawaiian islands chain. Very mountainous and either barren or covered in tropical jungle. I'm open to adding several more islands to this continent; I just sketched out a minimum. This also is one political entity, a single country as well as a continent.

I'd welcome any help provided, from hints and tips up to completely finishing this up for me!

This is for a roleplaying campaign I am writing, and while I have some time before the map elements become critical to the story, I'd like to have it done as soon as I can.

I have it as a photoshop document, at twice the resolution of the attached image - and including many layers of failed attempts to flesh it out. If you'd like, I can attach that as well. But I think it is much uglier, and this is probably just as good (or better) as that.

THANK YOU, for ANY help you're willing to offer!!!