As a photographer, who has had this happen with my images, specifically musicians, I’ll describe it from the original artist’s perspective:
The original (gorgeous, I’ll add) portrait took some work. It’s not just a snapshot. The photographer had to gain access to the subject, schedule the shoot, work with the artist to get a great shot, then, process the image, and do all post-production work. A high-quality image like that takes time and know-how. Basically, how would you feel if you, having developed your art to a high level, have someone come and take it, and pass it off as their own work?
Photography has always suffered from the perception of, “Ah, anyone can do that, click, click…”, but I’ll attest to the fact that it is intense work to get a great image. A good photographer puts their heart and soul into their work as much as any other artist, and that should be respected. As said on this thread, there are legal strictures in order to protect artist’s rights.
In your case; a fine interpretation of the original photograph, but definitely derivative. If I were the photographer, and saw you selling that piece, I’d immediately recognize it, and be rather pissed. This, did, in fact, happen to me; a local artist did a pencil drawing from a photograph I took (again, not a snapshot, but a carefully composed and worked for image), and exhibited it, for sale, at a local gallery. Her reputation was bolstered by that show, and that piece looked like she had the intimacy of subject that I had worked hard to achieve. I’m not a hard-ass, so talked to her about it, detailing the same issues as above.
She honestly had no idea of that sort of infringement, and liked the photo, so copied it, with good skill. She didn’t even think to ask permission, which would have been easy, as we were in the same area, and she knew it was my photo, and that work was my forte. I understood her innocence on it, educated her, and asked that she should always contact a photographer before doing that again. Could have had good basis for a legal suit, but, what a sad mess that would be.
One more issue about your specific case; that site, provacatueuse.com, from what I could see, is violating copyrights willy-nilly. Most of the photos there are professional images that are lifted onto the site, without credit. Photographers would be not happy with that. It’s hard to keep track of it, perhaps impossible, with internet ability, but common courtesy requires at least crediting the photographer.
I hope this at least lets you see what is at stake for all artists. Someone could easily lift your work and use it to illustrate their webpage, without giving you credit. Respect of another’s work kept in mind is key.