I don't know if cards are appropriate or not. I don't think I would give my therapist a card as it'd feel wrong or inappropriate somehow to me.

I did read once that it's inappropriate to give any kind of gift to a therapist. Here's a webpage that talks about that:

http://www.guidetopsychology.com/questions/q_gift.htm

That's more about gifts than cards though. But there might be some crossover so it's worth checking out....

Sidony