First off I want to say that me finding this was inspired by another member on this forum (The_Dragon69) . He found an image in the upper right corner of the old character roster poster.
I began looking around and I found more faces in that picture and one in the MKA site wallpaper. I have the links below and I used paint to outline and draw attention to the faces. I also have the originals so that you can compare. The site has been so busy that it's frustrating me into just starting this thread rather than finding the original one.
The link below is the original roster for mka.
http://www.esnips.com/doc/a871c1a7-6f46-4a82-8488-fc12f3fcdd8c/MKAwallmidwayfix2.jpg
http://www.esnips.com/doc/5741eb9f-5e79-4945-948b-72f0e8c1f30f/MKAwallmidwayfix2-faces.jpg
The above site is the mka old roster with 3 faces not counting the assumed chameleon image in the upper corner.
http://www.esnips.com/doc/658acfdf-8215-4984-bc10-5e05bd6f8bc6/darkface.jpg
This last link is very very hard to see so I drew a copy of what I saw in the lower right hand corner. I know it's cruddy but it's the best i can do with paint. I circled it and made an arrow.
For most of these you will need to zoom in a bit to see what I mean.