if you sell that shirt with the design on it...and you didn't design it...you can be sued by the original designer.
'dems the facts.
More to the point: if your work is an unauthorized derivative work based on a copyrighted work (like, for example, Willie) owned by another (like, for example, whatever part of KSU's Athletic Department owns Willie) you (like, for example, Thujone) cannot register a valid copyright in your infringing work (like, for example, the clearly infringing Murderer's Row graphic). I'm sure BSAC will be along shortly to confirm but since Thujone is obviously a sock it really doesn't matter anyway.