As with many of the later ESB releases, Dengar was only seen on screen for a few seconds so the catalogue of images Kenner had to choose from was small. The image of Dengar is taken during the ‘bounty hunter lineup’ on the Super Star Destroyer.
The Dengar photoart seems to be true to the original photo, having not required any airbrushing or manipulation.
The image is fairly fuzzy and low resolution, which has transferred to the cardback. This probably shows the lack of stock images Kenner had to work with for the character.