definitely fill the space in with some shading. maybe fill the tribal with some brights like reds and oranges, and fill the background in with darker colors like navy blue. my friend has a similar sleeve that looks great.
part of the problem with yours is that tribal looks a lot better if it’s filled in/shaded, rather than just an outline like you have. throw in the fact that yours is just wrapping around what seems like older tattoos, and i can see why most people are in agreement that the blank space needs to be filled in.
anyway, just my two cents.
