RedAndCosmoteer
Well for the first Iteration I tried using a 5600x4800 pixel map, but... that didn't work out well. then I asked G4L4XY to find another one, who wasn't unholy gigantic, and he found this one, which is 400x278, it works fine, after submissions stop I might change map, stretch this one out bigger, thing is, I didn't use the other one because the forums wouldn't accept an image that big, and I don't know the limit of the forums...
I use GIMP, Usually I create a new layer for each faction, and use the pencil or the bucket on a selected area with a certain opaqueness to fill up the territory.