Old faithful is the most visited feature in all of Yellowstone. For the life of me, I don't know why. I've seen it in just about every season and it has an appeal, which to me is mediocre at best. If I had to pick a season I would choose winter, at least you won't be mobbed while you compose your shot and wait for the eruption.
Perhaps you can break the mold here. Perhaps a star lit sky with light painting of the geyser as it erupts. Just go for it and amaze us all.