Well, my first two thoughts are:

1) Minimize the polar land masses and maximize the temperate and tropical land areas. There's a greater variety of life in those in those regions.

2) Maybe save the borders for when you have the map finalized. Depending on the detail in your actual map, excessive backgrounds and borders can be distracting. Also, it depends on what look you're going after. Antique? Scientific/technical? Atlas?

One other thought...I like the idea of thinking of the place as an actual planet, and thus the circular hemispheres, but it's very hard to visualize actual land area on a hemispherical map. Is there a reason you've not plotted out the map on an equirectangular layout or other projection?