I think we need a giant mural on the facade of Memorial Stadium that commemorates Callahan's tenure at Nebraska. It would depict Bill falling (without a parachute) at a rapid pace, with a very panicked look about him. The background would be a typical blue, partly cloudy Nebraska sky. In lieu of the sun, we'd see the smiling face of Steve Pederson in the upper right-hand corner of the mural with rays of pure holiness radiating outward from it, and the ground would be replaced by the word "MEDIOCRITY", which would span the width of the facade.
Hell, T.O. has a statue AND the football field's named after him, and Devaney had a sports arena named after him. Surely the powers that be at the University realize that Callahan's contributions mustn't be forgotten.