one of the easiest is to transfer photos to fabric then sew the fabric into the quilt. There are books and videos about how to do this if it's something you want to pursue. Here's a link to one godzilla quilt that has been made (to give you an idea of what you can do):
http://makezine.com/craft/rad_godzilla_quilt/
Depending on your son's interest, you could have black and white outlines of godzilla and related shapes transferred to fabric then have your son color them. When fabric colors and pens are used and properly heat set, these blocks work very well.
There are patterns for quilts which would allow you to show off these blocks - BQ quilt by Maple Island Quilts is one of my favorite simple quilts and it would let these blocks show well.
Lots more ideas out there. good luck.