Hrm.
I don't really know the finer points of paypal, so I don't know if there's anything you could have done with them. But what I know you can do is this...
Make a listing with photos of the custom order, saying of course that it is a custom order. Make sure that one of the payment forms you accept is "other," which is usually for people who would like to mail a check or whatever.
Ask your customer (or anyone, really) to purchase the custom listing and select "other payment." Etsy will expect that customer to send you a check, so no eletronic payment will be necessary. You will have to pay for the listing fee and 3.5% fee, though. But at least your pictures will be out there, now.
Although it's riskier to you as a seller, it might be wiser if you don't ask for payment up front next time. Just tell them to give you as much time as you need to make their item and then make a custom listing for them to buy in the first place. ^-^