The musician and standard/totem bearer are sort of featured in the main age of Sigmar book already, on the page detailing the structure of the Stormcasts. I would prefer more of a flag style banner than something like the Lord Relictor's pole thing though. I'm sure in teh artwork there is a proper banner, sort of like a bigger version of the thing trailing from Vandus Hammerhand;s hammer (Lord Celestant on Dracoth).
I would be surprised if we see another Lord-Celestand on Dracoth miniature, but I would hope we might get another Lord-Relictor, and the Stormcasts definitely need some kind of Wizard, not just to cast spells, but to be able to unbind spells. And also benefit from the scenery bonuses like the occulum thingy