You can always test it by making a window the size of your finished block, 1/4 of the posy and see if you get design or solid color. Put two mirrors at an angle and reflect the square to see if it gives you enough design. Even one mirror will help you see.
Some computer literate people or people with a copy machine, take one square, copy it four times and see what they have when they assemble the posy. Or you could copy a paper sized piece of your fabric and cut out your finished size and assemble several.
They certainly are beautiful. I would think any of the florals would work. They sure are pretty