Here, the chopped up and reassembled flamers and burst cannon resembles a Cyclonic Ion Blaster and a shield was stuck on a plasma rifle to give it a more 'armored' look. The top bit represent the Command and Control node but that is not relevant in the new edition anymore so I'd probably proxy it as a Positional Relay or perhaps just a shield generator. The head has a bit of modification from a Target Lock unit. Overall, its pretty much a 'no-frill' conversion, not too much to stand out but enough to make a difference.... currently working on my second commander now and will post up as soon as he is ready!
http://sidestreaker.multiply.com/photos/album/89/Tau_Commander