Basically card from a Tarot deck at first glance... but something is decidedly odd about it. If you concentrate on the card, it grows cool to the touch. A little more concentration, and the card gains depth and movement, as the subject you saw moments before as a still image aquires life, and you are now in mental contact with them, for better or worse.
Trump is an ancient art, predating the Drawing of the Pattern or the Construction of the Logrus, and while in Amber it is a skill practiced by few... in the Courts is something akin to an honored trade profession, like that of a gold or silversmith, with the exception being the younger members of Chaosite society, where avante garde trump artists are frequently activists and deviants by the standards of the 'establishment'.