This post will hopefully give light to how I feel the map should be geographically and climatologically, though I'm not an expert in either so any help to make it more realistic would be appreciated.

I'll start with the westmost island. The mountain range is perhaps a bit exaggerated, but there are supposed to be much softer mountains there. The climate is similar to Great Britain, though a bit warmer.

The western mainland nations are more Mediterranean with hills, plains, etc. The river system is fine, though there are more tributaries. As we go east, we enter steppe region, dry, not unlike the Pontic steppe. Then the desert has rolling hills, mountains that prevent winds and moisture from entering as well. This can be mostly approximated by the Sahara no doubt.

The eastern nations climate are a bit more up in the air. They should be a bit hotter, especially more southeast, though temperate is also possible. Possibly some wooded areas further north.

That southwest island is tropical, the inner regions more so, the outer regions and the mountain ranges perhaps approximating the Andes as in South America.