I'll call it Christmas if I want. Sometimes political correctness is more harmful than good. (And sometimes holds a double standard)
I'm a freaking Buddhist and I still celebrate Christmas. It's a traditional holiday that isn't religious for everybody. Christmas has become one of those traditional holidays that you get out of it what you want to get out of it. If you dig commercialism - you'll go mad over spending as much as possible. If you dig generosity - you'll help the poor celebrate Christmas and aim to give. If you dig Christianity, you'll go to church and you'll pray and make it a special time in celebration of Jesus. If you dig family values, you'll make it a special family get-together - you'll probably give presents.
But...maybe that's a tangent. Sorry.
The cards look cool, though perhaps a bit over priced, though I can't think of many people who'd appreciate them - I only really know 1 Left4Dead fan, so it wouldn't be worth the money...or at least he's the only person I know that talks about it.
On that note, we need some TGC Christmas cards! I am fairly sure in the UK it's still Merry Christmas, so good thing TGC are mostly in the UK.