I am almost as hardcore as Scott Bourne when it comes to image theft.
The first mistake under valuing your work. You should have billed at least 4 times as much. Even if you are doing a trade for credit deal. You want send an invoice stating the value of the image stating how the image maybe used.
There are a couple of reasons for the invoice and the higher value. In your case they did not give you credit so you now have a worth while value to negotiate with or go to court with. By under valuing your work you now negotiating from a point of weakness. Also The company you are dealing with will pay more attention. To them your image has no value as of now.
In this case I would register the image immediately. Have a Lawyer write up a formal letter on his letterhead demanding the removal of the image, with the invoice and send it to the company in question, the web design company and the IP. If you have the image on Flickr make sure the image is set to all rights reserved
not Attribution Creative Commons
.Attribution Creative Commons has to be the dumbest setting for any pro shooter to use
Depending how deep your pockets and how much time you want to spend is what you need way on this one. Since the image has not been registered you will not find a lawyer to work on contingency. I would send an invoice that is charging them for the usage of the image on a daily basis, back dating since the violation of the agreement.
Gavin, I do think it is a little ironic that you have done a 180 from http://prophotoshow.net/forum/index.php/topic,1544.msg8878.html#msg8878
A couple of the things, that, I think that is missing from learning from just books and the internet is hands on experience, with working with gear and the experience and techniques of a good instructor. I have said before and I still will say it that classes and workshops is a more efficient way than self taught.
I am self taught in many areas, but I also was lucky to have many great instructors.
I looked at your ad. I liked what I saw. I like the concept. I see two areas that I would change. You tend to shoot for large wall display, which works well with wall prints, but in an ad it does not play as well.
I would say use a photo for the wall portrait in which the group is closer together with cropped tighter together. The big reason is that even with a glossy magazine tiny faces tend to become just dots with reproduction. So the full impact of the image is lost. If you were playing the image full page or double truck then the image you are showing would play better. but in the add it is played small.
The other minor concern is it is a very busy ad. so maybe a tighter crop to show off mantel and/or some creative burning in to direct the viewers eye.