From the strict Jain spiritual view: yes, it can be a cause of karma-bondage if the necklace or photo is kept out of attachment, possessiveness, or emotional dependence.

A Jain laywoman may keep and honor her mother’s memory, but:

• loving remembrance is one thing,
• deep attachment (rāga/moha) is another.

So the strict answer is:

If it is only remembrance, not a grave sin. If it feeds attachment, then spiritually it is not right and is karmically harmful.

In Jain Dharma, the safest path is to keep the feeling pure, grateful, and detached, without clinging.