Intertwined_Hearts
This thing was made with Tinkercad. I found that $250.00 minimum from most Wedding card places was a pain, and since I only needed 20 invitations, I decided to seal the flap with 3D intertwined hearts.
They are small, if you double the size (x,y,z increase to "2") and use a brim of 3mm, it makes the hearts you see in the picture (the brim makes it easier to apply the superglue agent to.)