Feels empty, how can I change that?

I’m exploring my style and I think I’ve sort of found i niche in this artwork specifically, but it feels it bit bland. Almost flat. How could improve it?

Any other crit is welcome!

I’m exploring my style and I think I’ve sort of found i niche in this artwork specifically, but it feels it bit bland. Almost flat. How could improve it?

Any other crit is welcome!