Anybody see the animatic in the blu-ray set extras disc for Episode III?
Basically, it was the wheel bike chase as envisioned by Spielberg. It is very OTT but would have been fun if it were finished. It also had Grievous finished off in an even nastier fashion.
As for the character's background, apart from the animated series his background was covered in novels such as Labyrynth of Evil. Basically part of the discontinuity between the portrayals of Grievous in the original cartoon is in part due to Lucas making revisions to the character in post, as well as changes in voice actors (Reportedly Gary Oldman was going to do the voice but there were issues with the Screen Actor's Guild).
For more info on Greivous here is the Wiki link
http://starwars.wikia.com/wiki/Greivous
Also here's an action figure spotlight on how he looked before he became a Cyborg:
http://www.rebelscum.com/TAC36grievous.asp
Some say the henchvillains in the films show the three aspects of Vader: Sith Lord (Maul) Fallen Jedi (Dooku) and Cyborg (Greivous)