After having bought the Sam & Max: The Devil's Playhouse posters from Laserschwert I've finally found a fellow local adventure gamer with an A3 scanner and can now offer high quality scans of each of the five episode posters:
Full size files at: https://archive.org/details/SamandMaxDe ... usePosters
Feel free to rehost.
The original posters were 17x11" in size, but due to the size of the scanner a few millimetres off the top or bottom had to be left out. Nothing with any artwork or text though.
Big thanks to Tomse from retro-commodore.eu for scanning and cleaning the images.