This is great. Something I noticed, because i ran into myself.

See the lines radiating out from the shore? How they become straight? That's from automating it in photoshop, (unless your using gimp).

example.png

For me, i would use the filters and such to get the right position as a guide, then just draw over it to avoid that straight line effect. There is so much great work going on, that if you can avoid those little digital footprints, I think it would put your work even farther ahead of the curve.

I know this is often a touchy area, it is at least for me. Might want to consider your choice of fonts. Find something that's less commonly used. Even if it means spending money. it will be worth it. the font in this one is more of a display font, then a copy font.

I'd also consider using 2-3 different fonts, to help designate different things. One for say geographical locations, one for civilizations. Sometimes just the same font, but a different color is enough.