The copyright for the screencaps used on this guide is most likely owned by the company or corporation that produced it -- MTV. Their use qualifies as Fair Use of the material under United States copyright law under the following auspices:
Their use here is entirely encyclopedic;
Their use in no way limits or hinders the copyright owners' rights distribute the television show in any way;
The image is being used in an informative way and should not detract from the original work.
No free or public domain images have been located for this TV Show.
Warning: Beavis and Butt-Head guide may contain spoilers