What can I do to stop someone who photographed my art from selling photos of my work online?

Step 1. Register the works that were copied with the US Copyright Office - www.copyright.gov. Step 2. Once registered, you are then ready to file suit against the copyist in Federal Court. Purchase one of the works as evidence of the copying. That way you have proof of infringement and who the seller is. A mere threat to them might be enough, otherwise be ready to fight. Look for a contingency fee lawyer to assist.

Sounds like a copyright violation to me. I would file copyright application(s) on your work and then contact an attorney about sending some letters.

A copyright owner has the exclusive rights: - to produce copies or reproductions of the work and to sell those copies (including, typically, electronic copies) - to import or export the work - to create derivative works(works that adapt the original work) - to perform or display the work publicly - to sell or assign these rights to others - to transmit or display by radio or video. Clearly, this person who is displaying photo images of your murals, is infringing your copyright. You should immediately advise the infringer that you own the copyright to the murals, your copyrights are being infringed by these photos, you would like the photos removed, and you will enforce your rights against this person if they are not removed immediately. Unless you have already done so, you should immediately register your mural with the U.S. Copyright Office. You can do this yourself, and you can register all of your murals together in a single registration. The forms are available online. Once the works have been registered, if the photos have not been removed, find counsel to represent you and have counsel proceed to notify the infringer one last time before you file suit.