This is looking fantastic, bartmoss. Are you still in inkscape at this stage? If you've moved to Gimp, then I would strongly suggest that you look up RobA's tutorial on creating not so precise coastlines (one of the useful tutorials for a workflow which starts in vector and moves to raster IMO). In fact I might put a link to it in my sig to save people having to search for it! The beauty of Rob's tutorial is that you keep the general shape of your landmass but impose convincing coastline detail (if that's the look you're shooting for).

Again, if you're moving your workflow into Gimp and want to give your mountains a less clean but more graduated feel, it's worth considering using the smudge tool to blend the colours a bit and then using a bit of dodge and burn to suggest shadows and highlights.

Really well thought out work bartmoss, I'm really looking forward to following this thread closely.