I normally keep away from commenting on WIPs for maps of this style, as I have little to offer (nothing, really!) when it comes to advice on drawing, but...
I may offer some comment on geography/history/economy/science behind this map? (suppose you answer yes, here goes...)
- The style and decoration (the lovely corners) indicates that this is a decorative map, made in a super-sized canvas/tapestry, commissioned by someone of importance;
- Like, say, those who benefit economically form the trade in that sea/channel or those who have recently conquered a vast part of it;
- Which means, the focus could be on sailing the channel;
- And how wealth and extraordinary the counties/kingdoms around it;
- And how diverse the lands connected by it are...
I don't know what are your usual steps towards a finished piece, but may I ask if you decided roughly on a scale (how big is the area shown?) and on a climate/biome (are there deserts/frozen forests/tropical marshes/whatever?).
And, lastly, I second Mouse on the compliment on those plateaus/precipices - they're SO WELL DONE!