That's great.

Chair-warmer is virtually the same as Russian "протиратель штанов" - (literally, workers who only sit at their desks and their pants wear off, or used as a verb "протирает штаны"...)
Paper pusher seems to me close to Russian "канцелярская крыса", or "конторская крыса" (lit., office rat), which has a rather negative meaning in Russian, eg it can be used emphatically: "Ты, крыса канцелярская!" (meaning 'you are a bloody bureaucrat and paper pusher!')
Bottom feeder is also great, perhaps it can be used in some instances in office environment.