For the line thickness, was thinking I may need to add variation to it, but had already done all the mountains, and that took so long and was not going to redo all that. Same thing with the coastal cliffs, have started messing around with that on my new piece, but had already finished the line work and colouring on this one. Will try both of these things out on my new map.
Secondly I'd try more variation with the line width on your next piece. A thinner line for the detail would really give the pic a lot more punch eg. mountain and tree detail). Some coastal cliffs on your southern landmass would also be pretty nice given the 3D view (similar to your southern most mountain plateau range) as otherwise it looks like 3d drawings drawn on top of an overhead flat landmass.