Like:

Mk1: -They have the Pacmans drawings.
-They have creators faces on the Botton of
the pit

Mk2: -The threes in the Living Forest are Boons
face.
-Noob Saibot means "Tobias Boon"

Mk3: -They have the Pacmas again in the cementery
level.
-They have creators names in the tombs of
the cementary.
-Johhnys Cage name is in a tomb.

Mk4: -This one is really cool, and I had read it
yesterday and test if it was true today. U
can see Shang Tsung face or some creator in
the "Raining level" when the lightins are
flashing a face is form in the sky.
-The level of "Fuenace stage"
shoes in, the walls
some faces of the designers of Mk4.
-"Elder gods face" is Richards Y. Ho.
MKDA: -The Portal Stage seems to be based on Disneys Atlantis movie.
Anymore cool hidden stuff U know about? Please, i would love to know, post here.