Yeah, the Fool is a tempting possibility because of that logo. The thing about cabala is that if you look at something that's complex and rich in information, you can almost always find elements in it to fit your favorite theory. And the artwork is very rich in symbolism.

If I wanted to support the idea that the Fool is the card in question, I'd point to the dog head on Adam's desk because the Fool card traditionally shows him walking with a dog. Also the wine in Maynard's photo then seems to suggest Dionysus or Bacchus, god of the vine, ecstasy, intoxication, and the god associated with the Fool. There is even a mention in Crowley's Book of Thoth of the Vulture goddess Maat being related to the French name for the card, Le Mat. Then there's the fact that the radio? on Maynard's desk seems to have its dial pointing to 11:00 and the Fool corresponds to path 11 on the Tree of Life. You could even say that the alphabet of daggers on the poster points to the fool because the Fool card is ruled by the element Air and the dagger is the magical weapon of air.

Since the Fool is the 1st card in the deck, there's nothing mysterious about it being the card on top if the cards haven't been shuffled.

Tempting, but I still think there's a lot more symbolism pointing more specifically to The Lovers.

Schism, the Lateralus song that deals most with the Lovers/Brothers symbolism even repeats "I know the pieces fit," a reference that sure makes me think of puzzles. And now on 10,000 days they continue to develop that theme in a lot of ways. I don't think I've seen another band carry themes from one album to another quite like this. Very cool.

Also, as an after thought about The Lovers:
In Adam's photo we see his hand sculpture on the desk.
In Justin's detail photo we see the same hand sculpture again, with the bird perched on it. And in The Lovers card, the two are being united in marriage by a third character, from another card: The Hermit. His primary symbol, derived from the Hebrew letter Yod is 'a hand.'