A lot of the vintage postcards are so pretty and have such charming sayings on them. Many have unique rhyming greetings, which you don't really see much anymore.
Personal printers and scanners make it easy to reproduce high quality images at home (If you don't have a color printer at home, a copy shop can do them for you at little cost. Just make sure to fit as many onto a page as you can). You can use these to make holiday cards, or you could even just print directly on a super thick card stock and send out postcards.
If you wanna make cards, here are a couple suggestions. I copied this vintage postcard onto two kinds of paper from my canon printer.
The top one is glossy photo paper and the one underneath is matte presentation paper. They both look really good and it was hard to tell the difference without touching them. The postcard on the glossy photo paper was a little sharper and had more contrast. It had a bit of a green cast to it. The matte photo paper had a bit of a blue cast to it. I think how you are going to use them is what might determine which paper you use.
The glossy photo paper is thicker and better to use like you would a photograph. An easy way to make cards with these would be to use photo corners and just place the copies like a photo onto blanks cards or folded colored paper stock.
If you want to decorate the cards more, using the matte paper would probably be better. It is thinner and easier to paste down. You could make some gorgeous handmade Christmas, New Years or any greeting cards by using the copy of the vintage postcard and then decorating with glitter, ribbon, vintage items or whatever you can think up. I am no pro at this, by any means, but I have done my cards like this in the past. I made one up today, just to give you an idea. I'm sure you can do much better.
You can use some colored paper to make the background have a little more depth if you want. After that is glued down I added some glitter.
If you want some better inspiration, take a look at the Little Pink Studio. She is always making something pretty and artful with vintage images.
I'd love to see what you make this year. Please let me know. Happy Christmas Season!