Mathieu, the wonderful backlighting makes this image. I love the way the petals look like paper. Awesome. I also like the dark background as it helps to make the flowers really pop. I could see a bit of a crop on the right to pull the flowers a little off center and leaning into the left side. Nicely done.
I would clean up the light spots or blotches in the BG and the light vertical lines can be cloned out. Also reduce the very strong highlights on the flowers. Play around with the highlights slider to tame them down a bit. I agree with the recommended crop too. Otherwise, the flowers are nice and sharp and the dark BG makes the lavenders pop…Jim