What is the ruling on wearing a silver ring (wedding band) on the finger? And if only the fiancée wears it and nothing is engraved on it, is that considered an imitation of non-Muslims?

The ring (diblah) forbidden for men is that made of gold, due to the Prophet's (peace be upon him) saying: "Indeed, these two [gold and silk] are forbidden for the males of my Ummah, permissible for their females." As for women, it is permissible for them to wear gold. It is also permissible for men to wear a ring made of silver or iron. However, the ring (diblah) in general is not from the Prophet's (peace be upon him) guidance, and it is better for both men and women not to wear it, due to the possibility of imitating the customs of disbelievers.