If your simply ask your customer, "How would you like to pay for that?"
Then, check their facial expression, for The Look. The Look that asks, "Do I have to pay the whole amount now?"
As soon as I see The Look, I immediately chime in with, "You can pay half now, and the balance when you pickup your completed order. Or, you can pay the full amount now. And if I have a good rapport with the customer, which is almost always, I add with a smile, "Then, when you pickup up your finished order, it will be a completely happy occasion."
If you collect anything less than half when the order is placed, you run the risk of turning your back room into an orphanage for unwanted frames. And no matter how good looking someone's kids are, no one else is going to want to buy a framed picture of them.
Demanding the full amount up from, may create a trust issue, so I don't push it. But if you do get full payment at the time of the order, it increases the likelihood that a second order will be placed at the time of pickup as they'll have a zero balance due. Be sure to show your enthusiasm when notifying the customer that her/his order is ready. This will hasten pickup.