My guesses:
T-shirt - NO.
Hand lotion - double NO.
Rounders variant - eh, not with different court faces, at the least.
Gaff deck - not impossible; E hasn't produced a new gaff deck in a long time. But I would think that they'd sooner make a gaff deck for their flagship product line, Artifice, than they would for Madison's Rounders.
Now, a GAFFED deck is possible. E stopped production on its stripper decks - perhaps this is a revival. I'm hoping it's not Invisible, Rising Card, Svengali or Forcing - they're useful but not as versatile. Marked would be REALLY sweet, but he's done that already with his Players deck at T11.
Another possibility: Madison's all into the gambling mystique, especially when he talked about his Rounders ability to be used as shiners. Maybe a revival of the shiner ring would be a sweet idea.
But I don't think it's any of that. I think it really is just another back color for the Rounders. Most people do play poker using a two-deck matched set, after all. The deck's a hit, sold out at least once - it makes sense.