I've altered the size and adjusted the position of the large southern desert. I extended the foothills and elevation of the southern mountain range. I figure the small rainshadow effect this will create, combined with the distance from the ocean, should allow for the existence of the desert. I've also expanded the size of the two southern tropical rainforests and a tropical region and forest to the eastern island.
I'm still planning on adding sparse trees to the savannas and probably some more forest to the eastern island.