For the holidays you can spend time trying to find an ornament you like or you can just make one yourself. I'm a fan of geometric patterns myself and am kinda tired of snowflakes so it's a lot easier to just design my own to be 3D printed. Even if you don't have your own 3D printer (I don't have one myself) it's easy to send files out to be printed elsewhere like at 3dcreationsystems.com. They're the ones that printed this one.
As for how to make the design, you can do it yourself with free online software. I used 123D Design to make this one. Here's how.
Step 1: Start With a Circle
This is a really short tube. 35mm wide, 3mm tall, and 3mm thick.
Step 2: Copy the Circle
Make a copy of the circle and move it away from the first one. Group them together and you have your first pair.
Step 3: Copy the Pair
Copy the pair of circles and rotate the copy 60 degrees.
Step 4: Third Pair
Now make another copy and rotate it 120 degrees.
Step 5: Align!
Use the align tool to center all the groups in both the x and y directions. Now group them all together.
Step 6: Shrinking, Pt 1
Make a copy of this group and shrink it down
Step 7: Shrinking, Pt 2
Now make another copy of the group and shrink it down even more. Here the three groups have been changed in color to see where they are more easily.
Step 8: Make the Loop
Now the the design is done we just need a place for the thread to attach to. So make another tube that is 9 mm wide, 3 mm tall and whose walls are 2 mm thick.
Step 9: Place the Loop
Move the loop into place.
Step 10: Align Again
Now align the loop with the rest of the design to center it.
And you're done! The design is ready to be exported for a print.
Step 11: Print!
Now print up the ornament! You can use a home printer like the MakerBot, but some of the details might get lost. For better detail a print with an online service in nylon will get cleaner results.