Okay, I know you said you didn't want to introduce another color but personally, I think that's what it needs. I love your leaves but I think I would make a large block of 4 leaves with sashing between them and a center connecting the sashings. I'd put the stems pointing toward the center.
You have so many different ways that you can use the leaves....... I just love them..... you can send some to me if you decide you have too many.