Monkey Island 2 back cover and MI posters
Laserschwert has been running a very interesting thread on the The Internal House of Mojo forums where he has posters from all Monkey Island games. The posters are based on scans from the boxes or official posters and are very high resolution. The images have even been used on commercial products like the The Secret of Monkey Island Premium Edition from Limited Run Games. They are also going to be used on the upcoming Monkey Island Anthology boxset which should be announced soon.
Recently, Laserschwert also added a piece of art from LeChuck's Revenge: Monkey Island 2 which is featured on the box back cover. This cover art is usually overlaid by text. However, he managed to get a scan from the Taiwanese instructions manual which doesn't have any text covering it and allows to see the whole art in all its glory.
Be sure to check out the whole thread here!
Update: corrected the information regarding the scan source. Thanks to Walter Vonder for providing the correct source in the comments.