The Jargon File (version 4.4.7, 29 Dec 2003):

pretty pictures
 n.

    [scientific computation] The next step up from numbers. Interesting
    graphical output from a program that may not have any sensible relationship
    to the system the program is intended to model. Good for showing to 
    management.


The Free On-line Dictionary of Computing (30 December 2018):

pretty pictures

   (scientific computation) The next step up from numbers.
   Interesting graphical output from a program that may not have
   any sensible relationship to the system the program is
   intended to model, but good for showing to management.

   [Jargon File]

   (1995-02-15)