First, why not do the face mask as a separate subtool? That will create more convincing forms and allow for more detail. Most of the time it’s best to do accessories as separate subtools. 
To get a better distribution of topology, you have some options.
a) Retopology - This will allow complete control over how the polygons are distributed and where you want more detail. It will also allow preparation for animation with proper edge flow.
b) Project All - This will create a very even topology. Make a unified skin of the mesh, append it as a subtool, and divide it until it has a similar polycount. Have only these two subtools visible. Select the unified skin and hit project all in the subtool palette. Your mesh is early enough where it should work well. You can get projection errors with some meshes. If you do get any errors, simply use the zproject brush to clean them up 
c) Watch the first vid on this page: http://www.zbrushcentral.com/showthread.php?t=61676&page=6&pp=15
Lot’s of cool vids in that thread.
These are all good things to learn, but I would still just make it a separate subtool. Mortal Kombat was my favorite arcade game for years, btw. :evil: