If that happened to me as a buyer, and the 24h service was the main, or one of the main points and I had talked to the seller and told them that and they´d confirmed that they could and will deliver within 24h I´d ask for a refund too. If it wasn´t a high sum and if the seller had, from their side, offered me a refund, I might not even make use of it though, but IMO the minimum a seller in such a situation should do, is offer a refund, especially if it was a job that becomes worthless to the buyer because of the delivery past the deadline. It´s called a deadline for a reason after all.
As a seller that´s the reason I usually don´t have the 24h option active on my gigs to be booked directly, but only per custom order, which means a customer who wants it, will have to contact me first, so I can make sure that I´ll only sell a gig with 24h delivery, if I´m able to do it. If I´d accept a 24h delivery but wouldn´t be able to stick to it, I personally would message the customer to tell them I´m sorry and explain the reason I can´t deliver and suggest them to either refund them, or, if the 24h part wasn´t all that important and they´d still be able to use my work when I´d deliver it, to accept a request for extension of delivery time (as to @catwriter 's post).
It´s surely bad business practice to offer 24h service if one can´t handle it (even unfair practice against sellers who can and do, in case one offers it, if one knows or has to take into account that one can´t deliver) and an ‘empty delivery’ is a bad idea as well - if the seller presented you a reason you can sympathize with (fell sick, accident, whatever), or you want to embody the good spirit of Christmas or something you could make your course of action dependent on how nice or not you want to be, but if it´s as you said, you´re well within your right to ask for a refund obviously.