I just found this on pinterest the other day:
Recommended sizes
Hospice bed 63" X 80"
Neo Natal 36" X 36"
Crib 34"-36" X 48"
Wheel Chair 36" X 48"
Nap Quilt 40" X 55"-60"
No idea if those are universal or not. It was on the internet, so it must be true, right?
I do recommend flannel for the backing; it's not easy for some people to pull the quilt back up if it starts to slide. And while the ties are good for some people, not everyone will want or need them.