Hey there! It's looking really good! I really like how the illustration is coming together. :D First of all... I'm not entirely sure what the bubbles in the background are, but they're drawing slightly more attention than the character. You could reduce their brightness a bit so they don't compete with the focal point. As for adding details without losing the value structure of your scene, just keep in mind that any details you add should stay within the same value range. Try to avoid introducing very bright colors into areas that are meant to remain dark. It's a simple example, but I hope it gets the idea across. :) Hope this helps!

