In Concierge there's also an assistant room steward. We always tip them.
I would imagine piano players, etc.
Thanks for the assistant steward info. I haven't seen any of the entertainers tipped on any of our cruises, though.
Here's the current list. I really didn't realize there were so many opportunities to tip folks until the group here starting listing the possibilities!
Tipping opportunities:
Room steward *
Dining room server *
Dining room assistant server *
Dining room head server *
Bar drinks from any bar **
Popcorn and snacks sold at theaters **
Drinks sold by roving crew at sail away party or at shows **
Coffee drinks at the coffee bar **
Roving beach drink servers **
Wine steward (sommelier) **
Spa treatments ***
Photographers at private shoots
Room service
Concierge hosts
Concierge bartender
Concierge assistant room steward
Palo
Remy
Cabana Host
Luggage handlers at port
Taxi/bus/shuttle drivers to and from port
Shore excursion bus drivers, hosts, meal servers, guides
Hair braiding on deck
* Standard gratuities automatically added to your account, you can change at your discretion
** A tip is automatically added to your bill at each purchase, you can increase at your discretion
*** Mandatory 18% tip added to your bill
Other positions you DO NOT tip and likely will not accept them:
Children's club counselors
Ships officers
The Captain
Customs officials

Characters (meet and greet or photo ops)
Guest services personnel
Entertainers
Counter/buffet food servers
Bibbidi Bobbidi Boutique