It looks very nice. Just yesterday I was playing with the idea to create a hearth Xmas calendar for my girlfriend but postponed it to next year :)

Only one hint: When designing for a 3D Printer my experience is that cutting the smaller hearths might look better then extruding them on top. The same applies to letters and numbers. At least the FFF 3D-Printer are not so good in printing fine details when the nozzle is too big. But the inverse is often doing quite well. 
But this a subject to a test print to see what your printer is best at and it depends on the size of the small hearts.