I made four of these window type snowflake pop up cards from Willem Boning's patterns. Unfortunately, he has taken the file off his site. (Although you can still get them from the Internet Archive if you know where to look hehehe.)
And fortunately, it's pretty easy to make similar cards!
I used letters from WWFlakes, a dingbat font, and added a few tweaks here and there.
Cut on the black lines. Extend the horizontal and vertical (center) cut lines to cut the four cards apart. Crease on the red lines.
More information about his kind of card here.
Extreme Cards and Papercrafting: pop up cards, movable and mechanical cards, digital crafts and unusual papercrafts.