The first three German translations of the Wing Commander novels used the same Paul Alexander paintings commissioned by Baen as their covers. Starting with Heart of the Tiger, however, the publisher began using 'slush' artwork that they happened to own the rights to reuse. As a result, four books were published with covers initially used by (and created for) for other works. The first two unlikely sources were discovered in 2015 and now a third has been located!
The German cover to Heart of the Tiger (Book 4) is a painting by Romas Kukalis originally appeared in 1993 as the cover to Turning Point by Lisanne Norman, the first book in the Sholan Alliance series. The German publisher mirrored the image, making it more difficult to search for mechanically! With this discovery, the remaining unidentified cover is the translation of the Peter Telep film adaptation.