There are a couple of threads that showed adding "shadows" to a t-shirt quilt. Here is a link to one of the threads:
http://www.quiltingboard.com/t-48453-1.htm
Scroll down to see the quilt that was done this way.
There was a more recent thread on the same topic with a photo of a different quilt, but I can't find it at the moment. For that quilt, each t-shirt was framed in gray and then shadowed.