Shower pipe is mounted on 3x6" subway tile 78" above shower floor (i.e. tub) and just below marble pencil trim tile. I think it could be a bit lower as I am petite and I think it looks pinched right under the pencil. Will be grateful for advice.

 

This is a pet peeve of mine. For some reason shower heads are mounted very high on shower walls (at least 60" from valve center line). Depending on the brand of valve set, there is a minimum height that must be met. When I remodeled my bathroom I lowered the shower head to 48" from center line of valve set. That was the max (or should I say minimum?) I could go. It was MOEN. However according to Am Std, their shower heads can be at any height from valve center line. My wife and daughter can't thank me enough for allowing them to reach the shower head.

edit...Forgot to answer your question. Get a handheld shower with a mounting rod that attaches to the wall. Then you can adjust the height to any thing you like.

 

They make longer shower arms that would bring the shower head closer to where you want it to be. Visit a plumbing supply store for this option, not a box store. It will gain you a couple of inches.

For what it is worth, the argument goes in the opposite direction for those of us who are on the taller side. Being able to get your head wet with out scooching down is a plus.

 

I have always preferred about 84" from the subfloor.

https://goo.gl/images/m0QJ6V

The bend of the arm and the size of the head factor into the final height but like Czizzi says, if it's too low for a tall person, that's worse IMO than being too high for a short person. Who needs to move the shower head once it's aimed in the right location?