Of all the Spirou covers created for Interpresse, this is in my personal view clearly the best. In fact, I tend to prefer it to the original Franquin cover!
Almost every element has been traced or possibly copy-pasted from that cover or from other Franquin illustrations (skillfully enough that it would take a better eye than mine to detect that it’s not an original), but I find the layout more dynamic than the rather overstuffed French version where only the Marsupilami really makes an impression, and the color scheme is much more atmospheric.
The other Interpresse covers were the work of Peter Madsen, so he’s the most probable culprit of this one too. But the picture is uncredited, and since it leans so heavily on Franquin, it’s hard to know for sure. Good work, whoever it was!