Here's an idea I'd like someone to work on and make a reality.
You have a small box on the table, the size of a deck of cards. It has, in fact, been painted to look like a deck of cards. It hinges open on one of the long sides.
(I can't draw.)
You open the box and remove two sponge balls and do a quick routine with them.
You shake the box and the spectator can hear change inside. You dump out three coins and do an effect with them.
You open the box again and show the spectator that it's empty.
(Seriously, dudes, I can't draw.)
"It may seem completely empty, but there's actually one other prop that I keep in here. My deck of cards."
With that you peel a layer of clear plastic tape off the hinged long-edge of the box, and it's clear those hinges were just a graphic under the tape. The tape also pulls off the top "layer" of the box, the painted card back on a thin piece of paper. You crumple it all up and toss it over your shoulder. What you're left with is a normal, examinable deck of cards.
This isn't really "my type" of idea that I would spend a lot of time working on and developing. This is more of something you'd see in someone's FISM act or some junk like that. But it is something I like, and I have a workable method for it.
It's kind of has a reverse "Solid Deception" feel to it. Which I would say is a good thing. Instead of a deck of cards becoming a solid object for really no reason, a solid object disintegrates into a deck of cards. And there is a pleasing logic to it. "I keep all my magic props in this box." And the box transforms into your final prop.
The idea started one day when I had a deck in my hand, cracked open like a hinged box, and I was pretending to remove stuff from it that was actually finger-palmed in my right hand or hidden under the deck. It looked pretty good in a mirror.
Then I thought that if you had a card with the image of an empty box interior on its face, and another card with the image of an empty box interior on its back, then you could put them together in the deck and crack it open at that point and show people an empty box. (Likely only briefly. I don't know how real it would look.) And if the two images were treated with roughing spray or Science Friction, then you could flash an empty box and when it closed it would immediately transform into an examinable deck of cards.
The clear plastic tape on the edge would keep the fake hinges in place and hold the deck together somewhat. You would also draw a straight black line along the tape which would pass as the break between the top and bottom of the box.
The image on top of the "box" could be stuck to the top card with repositionable glue. The purpose of that image is you don't want it looking too much like a deck of cards from the start. In fact, maybe it's not even a painted card back. Maybe it's some other image all together.
You could have some kind of rattle gimmick to produce the sound of the coins.
As I said, the items to be produced would be finger palmed. Or, in the case of the coins, perhaps held in the hand under the box and then apparently dumped out of it. Or you could maybe do some kind of Han Ping Chien type maneuver to dump them out.
This idea supposes a couple things which might not be true:
1. On a brief glance a picture of the interior of a box could pass for the real thing. I think it would, but can't say for sure. I'm less concerned about the fake hinges, even though they're in view the whole time, because they would be very small. And, if nothing else, you could use actual tiny hinges stuck to the deck in some way, and then just pluck them off.
2. That the side of a deck of cards wouldn't immediately give away that it's a deck of cards. Maybe you could stain it or something? I don't know.
Go work on it and let me know. I can't do everything here. I'm just the idea man.
What I like is that you get the transformation with no switching. But if you wanted to push it further (for your FISM act) the ideal ending would be to then switch the deck for an actual box with a normal Bicycle back graphic on top. You do your final trick, get your applause, then open the (switched in) box and place your props back inside. The crowd goes wild. You step to the microphone. "This act would not have been possible without the greatest mind in modern magic... Andy at The Jerx. So thank you, Andy. Or should I say... thank ME! That's right, I'm the Jerx!" you say, and put on a mask to hide your identity. Eugene Burger leans over to Jonathan Pendragon and says, "He knows we could see his face the whole time leading up to that, right?" And then you mysteriously vanish.