I knocked this out in Photoshop in a few hours, including a lot of loafing around. There are probably a lot of goof-ups and artifacts in mine, because I was pressing for a quick finish and "how would that work?" rather than perfection.
The basic landmass outlines were done more or less similarly to other people's ideas on how to do so, though I scrubbed out textures onto the base forms by hand because with a big enough brush I just like it more for control. Then I doodled out templates for the base shapes, a mountain template for the mountains, the One Tree by which all trees are formed, etc. Then I resized them to be tiny, copied them, and banged out everything in a Paste--->Move fashion (sometimes making larger groups to make it easier) and it was done pretty quickly. I tossed some watercolor and colored pencil effects on the grouped and merged shapes, and finally finished it off by desaturating it some because I thought it looked a little more like a computer map with the brighter colors than I was happy with.