We as a group have discussed a format where the only cards you can use are “tattooed” cards for a long time now. Some of our brightest minds, and several of our dimmer bulbs, have finally come up with some rules and standards.
I present to you Old Order Old Schools Tattoo40!

Introducing Tattoo40: the newest extremely niche old school format.
Deck construction rules:
Atlantic B&R including reprint policy, 40 card deck minimum. All cards besides basic lands must have been obtained as event prizes or participation cards from attending events (stamped, scribbled on by participants, etc).
The aim of this format is to have a fun way to show off your otherwise less useful prize cards. These decks are intended to be used in pick-up games, not stand-alone tournaments.
Old Order Old School has been testing the format for a few months and it seems to be pretty fun, but obviously it’s not for everyone.
Q1: What if I don’t have enough cards to build a 40 card deck?
A: Attend more events.
Q2: What if my friends and I get together for a 3 man event where everyone gets a playset of Serendib Efreets as a prize?
A: The “don’t be an asshole” rule applies here. If you can make a genuine case that you won a card in an event, please play it.
Q3: Are raffle prizes legal?
A: Yes, if it was a card given to attendees of the raffle. Cards you won in the raffle itself are not legal.
Q4: What if I buy prize cards from ebay to use?
A: Refer to the answer to question 2.
Q5: What if I bring cards to events to have my opponents sign for fun?
A: If you didn’t obtain it from the event itself, it’s not legal. I realize this is impossible to enforce, so refer to answer 2.

Now get out there and attend some events and hunt for the next tattooed card for your Tattoo40 deck!