I've been wanting to do this design ever since I bought those heart shape craft punch some time ago.....it came in 3 different sizes....same shape but different size. I don't know why but this kind of layout is something that I just love doing. I've done something similar to this before way back in 2010 or earlier than that I can't remember, like my V021 card where I embellish the whole card with heart shape patterns....filling them up until there is no room or other embellishments.
Back then, I didn't have any heart shape craft punch so I basically had to cut the heart shape patterns all by hand using just a pair of scissors. It was very very time consuming but I enjoyed it because I was able to make any heart shape size pattern I liked. It was not practical for mass production but very satisfying as a crafter :).
I really like the pop up hearts I made inside this card. This is the first time for me to make this kind of pop up where the top part of the pop up and the bottom part is the same and it comes together in the center when I open the card. I love looking at how it moves to the center. Fun! You can view the pop up hearts in motion at the video I prepared below. Do check it out! ^.^