I've never seen anything on patterns for the megaminx, with the
sole exception of Kurt Endl's book "Megaminx".
It is long ago I had it in my hands, and I have no books. What I say
is from memory; probably correct. Note that a face turn induces an
even permutation on both the corner and the edge "cubies". So odd
permutations are not possible. On the other hand (if I remember well)
*all* combinations of even permutations are possible.
There are 6 opposite pairs of faces on the megaminx. There are 4 ways
to rotate the centres for each pair to generate a 10 spot. I'll
speculate that there are 6*4 = 24 possible 10-spots.
I suspect various 12-spots are possible. I have no idea how to
easily permute centre pieces on the megaminx.
Indeed. Every rotation of the center skeleton is possible (if you
consider the remainder fixed...). So there are 12 centers that can
come out at top; for each center at top you have 5 possible positions
of the remainder leading to 60 configurations. Of these 24 are
10-spots, 1 is the solved puzzle, so the remainder (35) is 12-spots.