Right now, I think her waist and lowerback feel a bit...empty (Disregard the tattoo, it's just there to temporarily cover my shame).

Speaking of empty, I feel I should add a background, but everything I can think of makes the entire thing look too cluttered.

Any suggestions? (No CWs, please! I'm completely broke atm ;v;)

I think a background isn't necessary, since there is already the red aura thing surrounding your HA, which fits well imo. How about adding a tail to go with the fox(?) ears? Perhaps something like or or ?