While I am licensed in Florida, your issue is one that not only deals with federal (and Florida) copyright principles, but other legal principles as well. While I agree with my colleague that the use of a famous quote may not violate federal (or Florida) copyrights, you must be careful not to infringe anyone's rights in publicity - the right to control and profit from the commercial use of one's name, likeness and persona. Your proposed commercial use (selling t-shirts that contain a famous artist's name, particularly when coupled with a famous quote of theirs) may be enough to trigger such publicity rights. Such rights continue even after the "famous artist" is deceased, but the courts differ on how long the rights survive. In general, such rights do not survive more than a generation or two after the person has passed.
This answer is for informational purposes only and is not intended to be legal advice nor does it establish an attorney-client relationship. You should consult a local business/intellectual property lawyer to obtain legal advice that is tailored to your circumstances and facts. Good luck to you.
Generally, short quotes, whether or not you attribute them to showever said them, aren't copyrightable.
Please see these many similar Qs&As: http://www.avvo.com/free-legal-advice/quotes#sort=recency
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
Personally, I think it's risky. It would not be a violation of copyright, as the first poster indicated, but may well either suggest an association between the "famous artist" and your company that does not exist or a false endorsement of your enterprise by the artist. It may also be deemed to violate the artist's publicity rights- i.e., the right to control the commercial use of their name or persona. In some states, publicity rights are protected by statute; in some, by common-law or court decisions; and in still others, by both common law and statute.
You should consult an attorney in the state in which you are contemplating establishing the business to review your business plan.
Disclaimer: This answer does not establish an attorney-client relationship or constitute legal advice. It is for general informational purposes only.