If you are concerned about your baby's safety due to polyethylene terephthalate in fleece, you may go for an eco fleece which is manufactured from 100% post-consumer recycled plastic. Depending upon the age of your baby and the intended use, you may choose a fleece blanket in any size between 30'' to 50''.
To begin with, collect pieces of fabrics in either cotton or busy. Cut the fabric pieces into squares of 2''x2'' and 4''x4''. Sew four 2''x2'' squares together, so that you get a single large square of size 4''x4''.
Another option is making a baby version of an adult snuggie. Simply attach sleeves to the blanket and make a hole for head. You may also attach a hood to keep your baby's head warm.
You may also enhance the utility factor of a baby blanket by attaching several small baby blankets with Velcro, so that it resembles a mini carpet. You can throw this carpet on the floor whenever you are visiting friends. This way, you won't have to bother about ruining your friend's expensive rug. Also, your baby will love playing on her familiar blanket.