how's that so? stage presence/image is definately an important part of being a decent live band. i've been many bands,while impressive musically, stood like statues onstage with little movement, on the other hand,i've also seen bands that weren't that good musically but got the crowd and energy level sky high with the intensity of the stage show. guess which turned out more enjoyable?
if these "gimmicks" detract from your ability to play the music properly,then dont do it. but if you can pull them off and still play decently,go for it by all means.
i think the best example would be the dillinger escape plan. completely insane stage show,guitarists and bassist all over the place,jumping around and slamming their headstocks into the celing,each other etc admist epilepsy-inducing strobe lights...and playing all the material NOTE FOR NOTE PERFECT. best live gig i've ever seen,period.