I bought an International Serenity 27FB last year and wanted an office setup for photo and other work. It wasn't hard. The rear dinette setup has a long couch on the driver's side and a shorter bench on the passenger side. Here's what the rear area looked like as Airstream built the rig:
I removed the short bench by undoing a bunch of screws, put down a chair mat to protect the cheap Airstream flooring, and put in a standard rolling office chair:
It makes a very comfortable setup for Photoshop and other work using my 15" MacBook Pro. (I used to use a 27" iMac, but since I mostly boondock, keeping up with its power needs was a chore.)