Dead Presidents is a term that refers to US currency bank notes because most legal tender is adorned by a President of the United States with the exception of Benjamin Franklin. Dead Presidents was also a cult classic movie in the 90's. This term was also poplarized by Nas in a song titled "Who's world is this" and in the song "Dead Presidents" by Jay-Z.
The skull on the president's faces are meant to resemble the "death of the FIAT currency" and our trust in money shifting towards crypto currency.
dead presidents /ded prezidents/ :plural n.
Definition of dead presidents slang : U.S. money in the form of bills specifically : DOLLARS First Known Use of dead presidents 1944, in the meaning defined above
1. Merriam Dictionary