All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
One of the well-established Sharee'ah principles is that all things are deemed lawful unless proven otherwise with religious evidence indicating the prohibition in this regard. Ibn Taymiyyah wrote, “I know of no difference of opinion among early scholars that whatever is not declared unlawful by religious evidence is deemed lawful with no restrictions. Many scholars have underlined this fact in the fundamentals of Fiqh and its branches. I believe that some of them cited the scholarly consensus in this regard or believed that scholars most likely arrived at a scholarly consensus.”
We do not know of any religious impediment to using the heart-shaped symbol or making heart-shaped gift boxes or any other items. It is lawful according to the principle that all things are lawful in principle.
Allaah knows best.