How to spot problematic pictures in a publication?
i once saw a presentation by a journal editor about what they do to check on modified, altered data. 

as you can guess, they ask for the raw data, and check imagies with photoshop. 

a very easy way to spot altered pictures is to blow up contrast and brightness, which tends to highlights cropped and modified areas.

obviously people are getting smarter at that too, but if the goal is to deceive, i think at some point it will be difficult to tell what's fake and what's not.