As a general observation (and one that could be attended to later I guess) I would add more islands - about half a dozen biggish ones around the size of your big purple one. I would also "Budget for" the idea of lots and lots of little ones as archiplelagos. At this scale they only need to be roughly attended to but later on, well, then it's detail time...
It terms of game play, islands are good for adding in the weirder aspects of the game tself, isolated areas for different stuff to have happened.

[This following point might be in the tutorials you've read! If so I apologise for repeating it.
When mapping for actual games you need to ask yourself what the maps you create are for. Are they handouts for the Players, and therefore very likely full of innacuracies - or are they reference maps for the GM, in which case, the opposite....? ]

just my h'penny worth!
cheers