I am very sorry to hear that your mother passed away. I'd go check out the t shirt quilt from
Teaquilts YouTube page. She has a quite awesome tutorial on making t-shirt quilts. Also, there are a lot of other fun ideas posted on there. It sounds like whatever you come up with will create a wonderful tangible item to remember your mother by. Please do keep us updated on the progress of this quilt. I bet it will be really cool.