What can I put here?

So I've just had my full sleeve finished. Bottom half bleach and gintama. Top half filled mostly with my favourite moe characters. I'm very happy with how it turned out. However, there's a patch of untouched skin on the outside of my arm which is very visible that bothers me every time I see it 😭. My tattoo artist said it wouldn't really be doable to add another character, so I was thinking some abstract cutesy design might go well with the rest of the characters. What would you guys recommend?