Is it permissible to say something other than "Amen," such as "Praise be to Allah" (Alhamdulillah) or "Glory be to Allah" (Subhanallah), when the Imam supplicates in prayer?

What is prescribed in audible supplication is to say "Amin," meaning "O Allah, respond." As for praise, the congregant either says "Amin" because it is in the context of supplication, or remains silent. Some jurists have recommended the congregant to join the Imam in praise, and joining is preferable, as it is remembrance and praise, for which "Amin" is not appropriate. Saying "Alhamdulillah" (Praise be to Allah) or "Subhanallah" (Glory be to Allah) is not prescribed unless it is to join the Imam.