The Drunken Bishop Algorithm
How the comparison is supposed to be displayed:  +-----[first]-----+    +-----[second]----+
  |       .=o.  .   |    |        ..=o   . |
  |     . *+*. o    |    |       o 0+.. o  |
  |      =.*..o     |    |        X.o. o   |
  |       o + ..    |    |       . * .  .  |
  |        S o.     |    |        S o  .   |
  |         o  .    |    |         o    .  |
  |          .  . . |    |          .    ..|
  |              o .|    |               .o|
  |               E.|    |               Eo|
  +-----------------+    +-----------------+

That's way too much alike IMHO. A more chaotic algorithm would create images that differ more substantially.