What is the ruling on keeping gifts from a previous relationship after repentance, and what should I do with the photographs I took of others before repentance, given that it is impossible to delete them?

If the gifts given to the woman were in exchange for a forbidden act, then it is not permissible for her to return them or benefit from them. Rather, they must be given away as charity or spent on the interests of Muslims. If they were not in exchange for something forbidden, then it is permissible to benefit from them. As for photographic imaging, there is a difference of opinion among contemporary jurists, and the preponderant view is that it is forbidden except out of need or necessity. However, keeping pictures out of need or taking new pictures out of need is not blameworthy. As for the pictures you took that you do not possess now, there is no blame on you concerning them.