I wonder if there is a Constitutional challenge here.
It would seem that the Government is attempting to hinder the Pursuit of Happiness portion of the the Constitution by asserting a self-presumed right to freedom of speech as if it (the government) has the right to freedom of speech. In a "representative republic" the citizenry are in control of the government not the reverse. The last time I checked the government isn't a citizen of the United States.
While the "propaganda" purported to show the results of smoking may be well intentioned, the reality is that the government is dictating how a business must merchandise itself. The display of OSHA and DOL literature is for the education of employees (a provision of law that protects the citizenry), the "propaganda" is not intended to educate but hinder and disable the business owner his right to the "pursuit of happiness" or as it was originally intended to mean, his right to provide for his welfare and that of his family and employees.
