Wow, that map looks cool!
Unfortunately I can't imagine any way to change my map into portrait format, as I don't want to change the look of the continents.
What I could do is, make the map even smaller, so that it horizontally fits the small screen (it would have to be 500 x 375, right?) Though that will certainly add difficulty with regards to legibility
I like the trees being green on the linked map! I'll definitely try that.