I made a quilt for my grandmothers' 90th birthday with signed quilt blocks. I used muslin ((wish I had backed it w/ freezer paper - good suggestion)) cut into squares then made into blocks. If I had it to do again, I think I would make the quilt blocks first and back w/ FP then have people sign them.
That's my suggestion. Lots of blocks to choose from too. Consider the album block. It's a great one for signatures.
Jane