if i added to it, i wouldn't add anything inside the flowers. it might make the motif "disappear" in a muddle.
if you have the time, energy and patience you might consider two straight lines around the inside of the square (at 1/8th" and then at 1/4").
if it still seems [to you] to need something more, itty bitty stippling or bubbles/pebbles to fill in the blank space around the flowers would make the flowers pop.
of course, most of us would be tickled pink to have accomplished the lovely job you've done so far.
it won't really
need anything else, so let your instincts and energy level be your guide.