Ask HN: Hacker christmas cards?

So it's getting close to christmas and I need to start sending cards to my clients to say thank you for their business. However, I don't want to send the typical christmas cards you find in the store because they are boring and forgettable.

Does anybody know where I can buy "hacker" christmas cards? Something with a technology twist or a perhaps a sense of humor? Valve sells great christmas cards (http://store.valvesoftware.com/productshowcase/img.productshowcase/TF2-HolidayCards/Zoom_TF2_HolidayCards1.jpg) based on their games and I am looking for something similar that can be sent to businesses.