I will discuss each of them in turn:
Their use will make a bad presentation good.
-no, this is false: just inserting graphics will not save a bad presentation.
There should be at least one graphic element on each slide.
-this is also false: the decision whether there should be a graphic depends on the content of the presentation!!!
They should be appropriate and relevant to
the presentation's content.
-yes, this is true and probably the most important rule!
They should be large enough to be seen by
your audience.
-this is correct! if they can't be seen then they're only confusing the audience!!!
They should only be used when they enhance the content of
the presentation.
-this is also true!
