Question
Hello. Is there any advantages to mulching my indoor plants (a coleus, some
begonias, a banzai tree, a rubber plant and a bamboo plant) with pine needles?

Answer
Lorelei, Mulching is a wonderful thing to do.  Mulch will keep water from evaporating on a hot, hot summer day.  Mulch will keep freeze/thaw from breaking roots during temperature extremes through the winter.  Mulch will decompose and contribute to soil fertility.  Mulch prevents weeds from sprouting.

But none of these is a problem of indoor or even potted plants.  Begonias, Bonsai, bamboo and Coleus grown in pots do not have any need for any kind of Mulch, whether from pinetrees or otherwise.

Perhaps there is some other detail you omitted from your question?