There are lots of mistakes on the covers of the X-Wing books. On the Krytos Trap (X-Wing 3) there is a picture of Corran's X-Wing (You can tell it is because it's in cOrSec green). However, Corran doesn't fly at all in this book, especially during the pictured mission.
The Bacta War (X-Wing 4): The X-Wings on the front are white and red - rogue squadron colours. However, in this book, the pilots have their X-Wings painted in their own colours. D'oh!
Also, on the cover, aside from the Lusankya, there are three star destroyers pictured. There should only be two! (The Freedom and the Virulence if memory serves).
Starfighters of Adumar: The book describes that when blasting out of the hangar, Wedge leaves first. On the cover, Tycho is pictured leaving first. (You can tell by counting the number of stripes on the S-Foils. Wedge has 1, Tycho has 2).