When you see a killer (a.k.a. free or practically free) deal on photo cards on sites such as TinyPrints and Snapfish, snatch them up...even if you don't have the perfect family photo yet. Here is an example card from TinyPrints with a photo.
Here is that same card as it would appear if you do not select a photo to add to the card. You can easily add a photo at a later date.
Target has printable coupons on their website for 20 free 4x6 prints from time to time, including right now. Create a collage to fit 4 smaller photos per print and you can get 80 free pictures to add to your holiday card designs, which should be enough to cover your holiday card needs for the year. If you've got some thick tape, that adds dimension to the cards and makes them look very spiffy!
If you've got leftover cards, you can use them again next year (or in a few years). There are often deals on these photo cards on sites like TinyPrints and Snapfish. Just because you don't have your family pictures ready to do doesn't mean you can't act on these deals.
Also think about purchasing photo postcards. The pricing of these don't seem to be as good as they should be (considering they don't include envelopes), but you can't deny the money saved by using a postcard stamp!
If you've got digitally savvy friends and family, a great option is to send an electronic holiday card. Last year I went through the steps of creating a Christmas card through a photo card site and then took a screen shot of the card in preview mode. I sent out an email to my local friends with the holiday card as an attachment. It was a great way to wish them a happy holiday...for free! I still used the blank photo card idea above to send cards to family and friends that I do not see often so I could write them a more personalized handwritten note.
Go get your feelers out for great holiday greeting card deals...it's not too early!