Another vote for The Soul Key. Lazy, lazy job. I'd be curious to see what other possible cover ideas were considered before they settled on this.
Losing the Peace has one of the worst, most awkward photoshop blends for Picard and Worf. It looks like amateur work. The overall concept and design for the cover is fine. I just can't wrap my head around why anyone would approve the characters' composition and poses. The heads and the bodies don't match up AT ALL.
The photoshop job on Before Dishonor was fairly lazy, too, in the sense that it was just a photo of Seven layered over an image of a Borg cube. I could do that in two minutes with photoshop. It didn't look bad, per se. Just wasn't very original. The real offense is the presence of a VOY character on the cover of a TNG novel.
I don't care much for novels that just re-use publicity photos without adding anything interesting to the covers. I also don't like covers that don't really tell you anything about the story. VOY's Homecoming and The Farther Shore come to mind.
I've always hated the design for the A Time To... novels. They weren't labeled as TNG. The only visual images were the small banner at the top and the little square with a character's head in it. It just looked all wrong to me. It didn't make the novels seem interesting.