As Tartan said, it does depend on the bed size and whether it’s for play or suit the time period of the dollhouse.
I’ve made lots of doll quilts. Favorite size is 15x17 or roughly smaller than a fat quarter if you want just one piece of backing. I’ve done applique, coin collections, 4 patches, pinwheels, rail fences— whatever strikes my fancy. Seams havent bothered me . The scrappier the better. And it’s fun to use those decorative stitches on the doll quilts.