I agree with trout that a lot of Bonham's sound came from his hand technique. he used a lot of wrist action which was common with the guys that influenced him (Gene Krupa, Buddy Rich etc.) his tuning was also influenced by the big band guys.
But the thing i loved about Bonham was that he took what he liked from his influences and never gave up HIS originality or HIS personal style. for example he used the largest sticks he could find at that time which gave him more volume and power, he always stuck with the supraphonic snare, once it was available to him he always used a larger bass drum (26"), he prefered larger cymbals, he was a fan of hand drumming which he incorporated into his solos.
I came to the realization that to try to perfect that Bonham sound was actually......well...... unBonham like.
but to be honest i try to get it as close as i can while maintaining my own drumming identity as well.