I have to disagree. Tarantino is quite the perfectionist, a trait also possessed by Sergio Leone. QT knows exactly what he wants, like Leone, everything in a scene is there for a reason. Of course QT is open to offers (from the actors) about certain things within a scene, but anybody who has watched his film should know that everything is just how QT wants it, hence it is perfect. One instance is how QT uses pop culture-related set decoration in his films to compliment the pop culture dialogue.
For example, in Reservoir Dogs, Mr. Orange tells his boss that Joe reminds him of "The Thing" a member of The Fantastic Four and what do we later see in the background in Mr. Orange's appartment? A Silver Surfer poster
Also in Reservoir Dogs, there are numerous coffins in the warehouse. There are four wrapped coffins representing the characters anonymity through their aliases. The white coffin seems to represent Mr. White. This coffin is not wrapped possibly representing how Mr. White tries to show what his is like, his inside character so-to-speak. he other characters remain tight lipped on who they really are (hence the covered coffins), Mr. White tells Orange his name, he is also ready to uncover other personal information.
In Pulp Fiction, whilst the scene is concentrating on "Honey Bunney and Pumpkin" in the diner, you can hear Vincent and Jules' conversation. If you look closely, you will even notice Vincent walking off in the background to go the toilet.
In regards to Leone, he would spend hours positioning the props, trying to make sure they are perfect to film.