All these images are free to print out and use.
I like the look of this Santa but it does have a few odd blacked in areas that I hope you can incorporate well into your work.
From Let's Doodle, a variety of coloring pages together on one page. These seem to be hand drawn doodles.
I can't find the original post to this beautiful image, but here is the link to it on Pinterest.
Simple in it's design, I know you can color it with enough detail, value and depth to make it beautiful.
Not specifically for adults but detailed enough for you to enjoy.
While not specifically Christmas, it reminded me of a stained glass church window.
Christmas movies are always centered around a small town or village, here is a cute one to color.
Dover offers a variety of different art books for printing, coloring, collage and more. Each week they offer a few pages for free. Join their email list to continue to receive notifications of what is available.
Another offer from Dover.
What do you do when the coloring page is finished? Well, you could easily frame it. How about taking a picture of it and send it to be printed out smaller for use in a greeting card or postcard. Consider cutting off the extra white paper and wrapping it around a white pillar candle, use a blow dryer on it to melt the wax into the drawing for a very one of a kind candle. You could do a similar thing with a glass pillar vase, just use Mod Podge to adhere it to the glass. Photo copy it onto iron on transfer paper and turn your artwork into a throw pillow or tote bag. If you are really handy with a sewing machine, you could transfer the images onto fabric and create an entire quilt - how beautiful.