Is it possible to be able to set an image for a Box Set that is different from the images for each of the albums contained in the Box Set
Yes
Use the 'Series' tag field to enter the box set name.
Create an audio view and make it a 'Category' type view.
In the view use category "Series" followed by "Album"
Add the box set artwork to the Series folder located in MC's cover art folder.
See location in Options->File Location->Cover Art
If you only want to see box sets in your view, you can make a rule in 'Set rules for file display' for Series is not empty.