Service is seeing the future.

Believe it or not you can tell the future. Not the kind of future telling where you know the lottery numbers and the next four presidents but the very near future. Here's an example: A two year old grabs a glass from the counter, little does he know the glass is half full with milk. Do you know what happens next? I don't have to tell you because you can tell the future. Here's another: A party of fifteen 7 year old girls has come to paint at your studio and they are all finished but not quite leaving. Can you tell me the decible level in your studio for the next ten minutes? Knew you could! You are very good at this.
So now I want you to use your powers and apply them to your customer service. Imagine how grateful a customer will be if you anticipate their needs before they even know they need something. Changing their water, giving them a new palette, stopping them from making a mistake that might seriously affect the outcome of their work. You have an intuitive sense of what is to come. Though most things are new to your customers, you have been on this ride before. You know what is coming. Your customers will be amazed at your precognitive skills. Remember use your powers only for good.

Is it I before E except after C? Or is it...

Have you noticed that rules only seem to apply when they suit the person that made up the rule. For instance the aforementioned rule applies in the word "receive" but not to the word "concierge" Yes, yes that's derived from French. That doesn't seem to keep it out of my English dictionary so the exception to the rule stands.( You can use the word "their" for your example if you prefer. Yeah no "c" to be found but sure enough the "i" stands mockingly after the "e"?) Problem being that most rules were constructed to save us from ourselves. Don't speed, don't do drugs, don't play with fire, don't mix water and oil, don't stand in the middle of an open field in a lightning storm. All good rules. I do recommend following them.
What happens when you don't follow the rules. We are assuming, of course, that the rules we are about to break are rules that were created by you. The rule to our rule breaking is that there is a good reason to break the rule. In the name of our customer. Take any of the following rules and break them at will:
Open early, or stay open late.
Wave your studio fee.
Accept a coupon that has expired.
Get a customers piece done tomorrow, no extra charge.
Run with scissors. (No don't, but I want you to keep your wits about you.)
Paint today, on shift.
Take a day off at Christmas.(ew naughty.)
Let someone start painting with five minutes left til close.
Don't charge extra to come back and finish.
Give a discount.
Letter someones platter. Pro bono.

I am sure you get the point. It is up to you to decide what rules must stay firm and what you can bend. The point is to decide how important the it is to be an oak and not a palm tree.
The customers will feel special, like they have an in. They got to go past the velvet rope, they're on the VIP list, they got an onion ring in their french fries. They get to feel special like you cared enough to bend the rules for them because they matter to you.
Here's the hard part.
You have to do it for people that may not be your favorites right now.
Oh I know, not an easy task. Why, oh why, would you bother with that ornery customer that keeps coming in and causing trouble. Because she keeps coming in. Because her story of you will be one that she tells over and over. How she is always treated so special. How you always take care of her needs. How great you were to stay twenty minutes late. You will become legendary! Caring so much about your customers. Doing all that they needed you to do and so much more. I hear you oh naysayer of naysayers, "No way she does that. She goes home, brews a cauldron with bat wings and eye of newt, then comes back to cast her evil spells on me.". Could be true, fun to think about but even if it is your generosity and compassion will not go unnoticed by other customers. They too will witness all that you are and are trying to be. They will tell the stories as well. With all those stories of good will circulating. How could anyone possibly not want to visit your studio time and time again. And isn't that the point?

Motivation is positive

It is in my job description to be critical. I can walk into any place of business and find 5 things that could be more efficient or better utilized. However, criticism does not motivate. It actually has the opposite affect. It dejects and deflates. Like it or not, as humans, we tend to be very sensitive to the critical even if it is true. We want people to dote on us, stroke our pride and notice the good things that we have done, however small. So, what is one to do if we are having a hard time finding something positive to say but we need to motivate our employees? I like to put it like this:

"Let's have a positive conversation about a negative subject."

This short quote gives you the opportunity to talk about a difficult subject with the goal being a positive outcome. Frame of mind is the key. If you help people understand that your goal is to fix the problem, not fixate on the problem, your outcomes will be more enjoyable. Help them to help you tackle the problem they created. Show them they are the solution, they only need to be shown how. Then when they fix it, praise them. Nothing feels better than feeling better about yourself.