Thanks!

Well, to be honest I cheated I started with a randomly generated map in PlanetGen, which outputs as equirectangular (planetgen is free software; i can't grab a link while posting from my phone but google should find it pretty easily). Then I took that equirectangular map and ran it through g.projector.win (also free software, by folks at nasa) three times for the mercator projection and for both polar projections (with latitude set at 90 and -90 respectively).

To go from mercator to a polar map is really difficult, because the mercator projection fails at the poles (it stretched to infinity and never actually gets to the pole). And I can't free-hand the stretch for equi --- so I cheat.