Could a spellcaster that knows the Banishment spell use that spell on their own party members as a means to return to their home plane?

Sure, but you can only do it for one party member at a time, and even then you have to maintain concentration for an entire minute or else they’ll just pop back where they were.

Quote from SagaTympana >>

Sure, but you can only do it for one party member at a time, and even then you have to maintain concentration for an entire minute or else they’ll just pop back where they were.

 
Can also just upcast to banish extra people. 

Upside: yes, it gets you back to your home plane

Downside: you don't decide where, so it can be very random.

Yeah, the specific location leaves a lot to interpretation. DM could have fun with that.

I'd allow it, however, return to their home plane for "normal" mortals is the prime material plane, banishment does not state to which place, or even better, to which planet, crystal sphere or whatever the target creature is banished to.

So, someone from Faerun could end up on Krynn or Athas... and they could end up anywhere on the respective world.

Also, each and every creature banished could end up on a different world in a different location.

Fun times.

Sure if the party is on a different plane of existance you can use banishment to return them to their prime material (home) plane.

To expand on the question, what if the spellcaster casts Banishment on themselves?  I don't see any reason that a normal concentration check wouldn't maintain concentration on the spell throughout the process.

Quote from ahofford >>

To expand on the question, what if the spellcaster casts Banishment on themselves?  I don't see any reason that a normal concentration check wouldn't maintain concentration on the spell throughout the process.

 Should work. Target is just one creature you can see.

Problem with the unpredictable location of arrival still stands.

Quote from ahofford >>

To expand on the question, what if the spellcaster casts Banishment on themselves?  I don't see any reason that a normal concentration check wouldn't maintain concentration on the spell throughout the process.

In this case it would be fine because the caster would be banishing themselves to their home plane from a different plane. The problem would come if they are already on their home plane - because in that instance - Banishment sends them to a safe demi-plane and incapacitates them - which would immediately end concentration.