Does anyone have further documentation on 'mris_divide_parcellation' ?  Is there a picture of what it does?  

It is referred to in the FreeSurfer FAQ

Q. How can I get a high resolution atlas of the cortex in Freesurfer?

A: This can be accomplished using 'mris_divide_parcellation'. You can pass your preferred max area of a parcellation and it will keep subdividing along the primary eigen-axis until no units are above that surface area.