Prezi always shows 'the orientation of the object in the pathelement'.
That means that if you rotate, say, a picture, and the path is to that picture, the audience will see it upside-up and downside-down, no matter how you rotate. If you want the audience to see the picture upside down, you need to use (well: not need, but it is the simplest way) the (invisible) frame: just place it round the object you want to show, and connect the path to the frame instead of connecting it to the object (e.g. the picture).
If you now rotate the frame relative to the picture (or the picture relative to the frame), this WILL influence the way the audience views the picture.
Using frames is also a good way to combine more items in one view: you can place the frame around both a picture and a heading below or above.
(Fellow user, not affiliated with the prezi team).