Try adding some acrylic paint and some water to a spray bottle and spraying on your color. Here I played with drizzling very wet paint over my spray and dabbing at it with a paper towel. I also added some spatter.
You can have fun with your painting even if you don't quite like the outcome. That's what experimenting is all about. You learn what you don't like which better helps you move in the direction of what you do like which is a good reason to be grateful for the things you don't like.
Above and below are actually part of the same background. In the above photo, you can better see the plain water spatter on wet paint technique. It looks like bubbles and is great for sea backgrounds. I also added some glitter swirls and some sparkly stars although they don't look very sparkly in the photo.
These are the background colors I plan to use in my final painting. The colors are bright, cheerful and peaceful. Art is such an emotional experience for me. Colors speak to me on an emotional level which is why I like this so much. I can't wait to try a salt technique for painting some pink coral on this. It's gonna be a divine sea atmosphere for my mermie and I can tell she loves it already. (tee hee :)