I think something similar to this may be my Father's Day card this year but it could equally be used for a birthday. We did this at card club too; the folded shirts aren't nearly as difficult as they look and make an effective topper for your card don't you think?
I used copier paper for the shirt, stamped both sides and then run through the Big Shot in a textured embossing folder before folding into the shirt shape. It is matted onto some Pear Pizazz designer paper and Pumpkin Pie and mounted onto Crumb Cake card stock. The sentiment is stamped in matching Pumpkin ink, punched and 3d mounted.