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.
It is impermissible to exchange photos between the fiancée and her fiancé in order to keep them and look at them because this matter involves grave dangers. Let alone that this act is unlawful, it results in arousing sexual desires. Moreover, it may lead to committing what is unlawful.
You should tear these photos because looking at them and kissing them entail arousing sexual desire. This matter is permitted only within the boundaries of marriage.
It should be known that the fiancé is considered non-Mahram for his fiancée and it is impermissible to exchange words of love and passion. Consequently, you should stop doing this and abandon it until your marriage contract is concluded.
Allaah Knows best.