I've had a box of old t-shirts sitting in the closet for years doing nothing but taking up space. They were old Harley t-shirts from when my nephews were toddlers and old t-shirts that I've work out. I was watching a design show and saw a boutique was selling t-shirts made into wall art for big $!! Ridiculous money! I mean 1 months mortgage payment. I saw how simple it was and decided I could do it myself. I don't do things small so I decided to make 16, yes 16 for the wall in my bedroom. It cost less than $15 to make all of them and I have enough materials left to make 10 more.
The styrofoam I used was 1 3/4" thick. You might have some styrofoam laying around that you can save from the landfill. I bought it at a home improvement store. It was 80% cheaper then buying it at a craft store BUT craft stores do sell it in smaller pieces so you may not have to cut them. I used an old electric knife to cut mine with no problems.