Is this a T-shirt quilt and then you want to add additional blocks with printed images or appliqued blocks? If it is, there are excellent youtube videos about assembling and stabilizing t-shirts for a quilt top. As for applique images, there is the option of machine applique. Or what about embroidered images? Can you get your hands on an embroidery machine? Urbanthreads.com has some awesome images for machine embroidery that would look excellent as a quilt block. Like this one:
http://www.urbanthreads.com/products...oductid=UT2581
I've made one t-shirt quilt that was a combo of knit and woven shirts and then backed it with fleece and tied it with yarn. Not sure if this is helpful, but good luck to you. What a great gift for your son!