Hello swiss,
I'm a photoshop CS user myself, not an expert, but enough to be a little bit dangerous.
1) I really like the seaward side of the coastlines with the gradient blend of light blue to deeper blue. The beaches as a glow effect look okay, but beaches don't form all along a coast like that very often. Usually it is broken up by rocks, cliffs, and other coastal features. Beaches tend to form where the currents slow to drop their sediment (sand) amongst other places. As for controlling your coastlines, you can use a preset coastline that is created by hand or computer rather than generating one with clouds. I prefer to control the shape of my coasts manually in maps, though I tend to use existing (rpg game) maps as a base for my add-on work.
2) I like the blending, it works. Hills and mountains could use a colour difference as well though, generally brown colours are used to good effect.
3) I think the icons might just need to be less water-colour like and maybe throw a stroke around them and/or some outer glow to give them more impact. Hard to say without experimenting.
4) I like the 'satellite photo' look you've got going there, with the addition of browns/tans for mountains/hills which would make it more like a satellite photo, I think it would look great.
5) The rivers and lakes. They appear to be raised rather than sunken due to the lighting effect. Is it a bright shadow or glow? It looks inverted to how my eyes expect to see rivers and lakes.
Best wishes, niekell.