If you have registered your art-work with the U.S. copyright office, you can sue for copyright infringement. You also can send a take-down notice demanding that the business cease using your artwork. If you have not registered, you can still pursue claims by registering your art-work, but you would not be entitled to pursue statutory damages and attorneys fees and, therefore, your claims would not be very valuable. Also, if you provided this artwork to this business pursuant to an oral or written contractual relationship, you may have a claim for breach of contract. The devil is in the details and you need to review the relevant facts with intellectual property litigation counsel. Sometimes a demand letter from counsel to this business can resolve a matter such as this and provide you reasonable compensation for your efforts.
As the artist you own the copyright to your original artwork, and have the right to stop them from using your artwork and pay you for the use they’ve made so far. My bet is that you haven’t registered your copyright. That’s fine – you still have your rights. It’s just that registering your copyright gives you more rights and options. Plus you should register before filing a lawsuit, if that’s necessary.
There are also some more facts to your situation that would be important to consider. For example, even if you didn’t have a written contract you likely had some agreement or understanding with this company when you were initially building their website. That will need to be explored to determine what, if any, contract provisions may be relevant to your situation.
In any case, it’s time to talk this through with a lawyer.
(949) 390-2717 - Of course there's more to it! Plus, we don't have an attorney-client relationship. This brief comment is for information only, and must not be relied upon as legal advice.
Glad the artwork is now down.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Depending on what your contract says (assuming you have one), you have the right to sue for copyright infringement. However, you need to register your copyright before you can sue, and you'll need to have that process expedited if you want to file a lawsuit sooner than later. You can also, of course, retain counsel to tell the business owner to Cease & Desist his infringing use or to pay you whatever sum you determine is appropriate for use of your work. Go see a reputable IP attorney and lay out all the facts so you have an informed idea of your options.
You might not own the copyright if this was "worker for hire." The customer might actually own the copyright for work you created at the customer's request, for example, a logo for the customer's business. Maybe not though. Read your contract carefully and review it with a copyright lawyer. You should do that anyway to avoid future problems with the next customer who does not pay. Please consult with competent counsel in your area for a more specific answer.
Seems you got a favorable response already. The DMCA is effective when used properly by both the website and the copyright owner.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.