max-height of the preview image element is set to 200px. This is generally not a visible issue when working with DefaultImageProvider, because it goes through imaging servlet, using the 'portrait' configuration, which is set to 240x160.
However, different image provider implementations — in particular when working with 'liberated' content apps — may not need to go through imaging servlet, and may provide images that are bigger than the portrait size.
In this case current max-height in CSS is 200px in the action bar; it should be in sync with imaging configuration, i.e. 160px, so that images are scaled down properly.