From Yoma 5b, it seems that he will again re-dress the kohanim (or, at least, Aharon and his sons) in their kohanic clothing.
Niddah 70b also mentions him (according to one version of R. Yehoshua's answer) as being the one to decide whether those revived at techiyas hameisim will need to be sprinkled with parah adumah water. [Although according to the explanation given by the Lubavitcher Rebbe zt"l (Likkutei Sichos 18:249), the point of mentioning him there is that whether he reappears alone or together with the Jews who died in the desert will be a factor in determining whether they need such sprinkling; according to this approach, then, the halachic decision won't necessarily be in his hands.]