If you make them square in a square with black fabric, the hearts would all be on the diagonal. You could alternate directions like zig-zags.
If you laid them in sets of 4, the hearts would look like petals of a flower. You could either leave off your last column (4 blocks by 6 blocks), or make another column of 6 more hearts. Or you could make two more hearts and put two more "flower" sets of 4 hearts each at the bottom. The last choice makes your quilt 4 blocks by 8 blocks, which is long & skinny, but if you had pretty side borders, it could work.