Try fixing the film first. I hear it creates very interesting results!
By pinhole, jnanian is probably talking about a 4X5 or 8X10 pinhole camera, not one that takes 35mm film. You would use either sheet film, or photographic paper (paper negatives). A larger negative will make it easier to manipulate specific areas of the negative. If you do paper negatives, you can draw/shade on the back of the paper to darken areas or even add a certain amount of detail if you wanted.
You can get some very interesting results from a pinhole WITHOUT destroying the negative anyways. Especially if you do things like make the pinhole too small for the "focal length", make an imperfect pinhole etc.