Now that we know that Shockwave is the big bad of Transformers 3, it makes you wonder exactly what he will look like. When the character was first created he had an alt mode of a Cybertronian laser gun that later changed to a Cybertronian tank in later cartoon series.
Will he retain a tank mode for the movies despite Megatron already claiming that alt mode? Too early to know but the guys at Team Pandora Box created some sweet fan concept art last year for the character that might help you imagine the possibilities. Below is a little of their Shockwave, the rest can be found here.