Juan "Monster" Martinez wrote a MaxScript to help create overall gradient maps for models
"It's becoming popular to overlay a gradient to give emphasis to more important areas of a character. (See DOTA2 style guide.) This script will take your object selection and apply a gradient in object space for each object and render it out to a texture. Your objects must already be unwrapped. If your character has a hat or other gear you'll want to combine the objects temporarily to get one map."
The script is posted in this thread