I like the mug rug idea. Do you know what the colors will be for his new office or school district? That might give you a direction to go. Or if he is no longer going to be in education what about colors from the current school district.
As far as a quilt goes, there are several options. We had a great teacher who left the district last year and someone made a t-shirt quilt out of school shirts. Do you know any hobbies or activities that he enjoys? There is this
https://www.missouriquiltco.com/shop...quarter-bundle that could be used as it is a neutral color palate or add in some yellow or other solid color. Possibly do a disappearing 9 patch.