Most of the online ergonomic stuff I have is in german but I just googled with ergonomics+workplace and found this link:
Ergonomics of the Office and Workplace: An Overview
which has information including diagramm of sitting posture at work. It's not just what equipment you have but how you use it and the correct heights etc for your body. There seemed to be lots to look at to get you started. Must look at it myself again.