PearsonArtPhoto's answer on "What's the coin on the Curiosity rover?" brought to mind the possibility of using a fractal-like image that could combine scale and color calibration functions and would be more of a work of art (suitable for posters).
Could such a pattern be a better (or at least equally good per unit area) calibration target? (Such would seem to provide greater information density and to provide more sensitive testing of color transition handling, but such might require more complex calibration software.)
Would such be excessively expensive to manufacture? (Ordinary printing technology might be excessively subject to fading or other damage and might not have the precise color control desired. The color samples on Curiosity appear to be plaques, presumably for damage resistance.)
Unifying function with aesthetics would seem to have at least some value in itself, even if the unification of specialized use with general appreciation did not increase the appreciation of the specialized use (i.e., it was useless as promotional material).