Find a copy of 9 patch pizzazz by judy sisneros, it's just what you're describing, and she has heaps of ideas. Have made several using her technique, and they are all great. Baby quilts can be as big or small as you like. Cradle quilts are more doll sized, cot/crib quilts bigger, but if you use one as a roll around/ play mat, then it can be huge. My grandchildren all received a cot siae one about 40 X 50", then another bigger for the floor, and then my granddaughter was made a pretty big girl one for her big bed. I don't think there's a rule for this.
excuse DH's socks
a little out of focus..sorry
this lives folded on a cupboard shelf now.