I like this a LOT. Don't have IML, but can figure out how to do it with Base SAS. (And actually, it was the Rob Rudis (hrbmstr) R implementation that led me here to the original source.)

However, I think this EDA technique would be even better if rotated 90 degrees.

(1) the variable names/labels, which often don't have concise but meaningless labels like x1-x55, are easier to read if they are written out horizontally, left-to-right.
(2) my impression (unsupported by any Google search for evidence) is that the human brain more easily compares left-side symmetry than up-down symmetry.