First off, your going to be very limited as far as a cover up(and i mean limited) So the best possible thing you can do is go to a very good artist(and i mean really good) to discuss possible designs, themes etc. It looks like a possible japanese or oriental dragon full sleeve can be achieved(but of course done by a professional who knows his shit)

What kinds of themes are you into?
and you said half sleeve, to be honest i think that limits you even more.

Take this lightly though becasue i am not an artist, this is all just my opinion on what i’ve seen over the many years of getting tattoo’d

Marcus