My wife used clip art similar to this (https://openclipart.org/detail/21285/valentine-red-maori-heart) to use for tickets to a Valentine's day lunch. Between this and a 3D-printable heart from Thingiverse (http://www.thingiverse.com/thing:18858), I combined the two ideas to get this design. They printed well and look pretty good standing up.
ValentineLunchHeart.stl | 3.6MB |