We might protest by stamping messages on dollar bills. I think it would be interesting to do things like print Guy Fawkes masks over the president's faces.
Or make bills say things like, "We are the 99%, so why do we have so few of these...". Or "Please don't put me back in a corporate bank!"
Draw blood dripping from the federal reserve logo?
It is not illegal to deface money unless it is rendered unusable. So as long as we leave most of the bill and all numbers alone, we are not guilty of any crime. Please correct me if I am wrong.
United States Code
TITLE 18 - CRIMES AND CRIMINAL PROCEDURE
PART I - CRIMES
CHAPTER 17 - COINS AND CURRENCY
§ 333. Mutilation of national bank obligations
Whoever mutilates, cuts, defaces, disfigures, or perforates, or
unites or cements together, or does any other thing to any bank bill,
draft, note, or other evidence of debt issued by any national banking
association, or Federal Reserve bank, or the Federal Reserve System,
with intent to render such bank bill, draft, note, or other evidence
of debt unfit to be reissued, shall be fined under this title or
imprisoned not more than six months