Every Scumskull is constructed from black or white pixels on a 5x5 grid. Additionally there are certain constraints on the shape of a Scumskull.

	A Scumskull must be symmetric to the vertical axis.
	A Scumskull must be contiguous. That is, all black pixels have to be connected. Diagonal connections are allowed.
	A Scumskull must be expletive. That is, the bounding box of the black pixels of a Scumskull must cover the whole 5x5 grid. Or, there must be at least one black pixel on the leftmost and rightmost columns and the topmost and bottommost rows of the grid.

An exhaustive search showed that according to this definition there are 12,209 possible Scumskulls.