A little review for people who currently have agents:
(1) Holiday card/gifts are by no means expected. They are simply what we like to call in the business "nice." If you are cutting back on things, by all means, skip the agent holiday card.
(2) If you do send a card and are wondering what denomination your agent is, go for a generic "holiday card." If you can't find one, Christmas is fine, unless your agent's name is Hebrewburg and she only represents Jewish fiction. Then Channukah is a pretty good guess. Or their name is Fatima al-Islam, in which case I wonder if they make "You don't have any holidays coming up that I know about because your lunar calender is on a different cycle this year but have a good time!" cards. (Is the Haj over? Does it apply to people not on the Haj itself or just make them feel guilty about not going on it?)
(2) If you are sending a gift, do not send perishables. Your agent may be out of the office and the fruit will rot. It's better not to send food at all, in case your agent is kosher/vegan/halal/Jain.
(3) If your agent has done a lot for you in the past year and/or you have a lot of upcoming projects they will be working hard on and you feel compelled to treat them to a gift, a Barnes & Noble or Amazon gift card is what I go with as a gift-giver myself, as I know my agent will definitely come up with a reason to use that.