Newbie requests suggestions (map attempts included)

[Nevermet]

Hello!

I found my way here because I wanted to make better maps for a pet project world of mine.
To date, I have exclusively used the techniques I've learned from RobA & Wisemoon's PDF tutorial on how to make maps with GIMP.

First, here is the basic map that I made using Autorealm and its gloriously simple fractal edges:


This map is of the Set Archipelago, and the map is supposed to be about 6,500 miles wide. This is the only land mass on the planet.
I realize the layout of the islands is likely not realistic, but it's how I want it to be. My only semi-regret about the map is that I would perhaps like to redo it so as to have some geographical features related to former glacial activity. However, as I know next to nothing about glacial activity, or how to do it in GIMP, this is not a major concern of mine.

Anyhow, from there, I opened up GIMP and created this map:


As I did more islands, I started to get a bit of a handle on how things work, so I started redoing the islands I had already completed. Each island I am doing as a separate file, and then scaling to the appropriate size and moving in place back on the larger map. Here is where I currently am:




So.... How am I doing so far? Sorry for the lame wording, but I still am working out what is the potential and relative difficulty of various actions in GIMP. I'm not sure what can be tightened up how easily.

That said, there are a few things I dislike about my efforts to date.

First, my forests sometimes look "plopped on" rather than part of the terrain.

Second, I don't really have terrain other than plans and sudden mountains. Foothills aside, I dont really get a sense of topography looking at my map so far.

Third, my mountains sometimes want to look like canyons rather than mountains.



Anyhow.... that's it. I haven't tried to do rivers yet, though I'm a bit nervous about them coming out.

Overall, I'm trying to work from an aesthetic similar to what a satellite photo would look like. I don't think this is by any means the only way to do things, but it's the way I want to do this map.

I'm open to suggestions, especially because I am too new to even know what to ask.

Thanks!