Unlike many copyright infringement cases, creating an illustration or painting of a photograph may not actually constitute a violation of copyright. Here’s why.
If the new image is based on a location or generic subject matter that is photographed often, there will likely be no violation of copyright.
Alternatively, an artist might draw inspiration from your style but add their own personal interpretation, thus adding their own creative contribution to your work, be it technique, or lighting style, or even combining several image perspectives into one. This would also not constitute a violation of your infringement rights.
“Fair use” is perhaps the most identifiable use of copyrighted material that isn’t an infringement violation. A creation is in “Fair use” if it serves the public good. “Fair use” applies when copyrighted materials are used in such fields as teaching, commentary, critique, or reporting. Unfortunately, this means that any satire your work inspires is also fair game, even if you do hold a copyright!
On the other hand, should an artist use a style (or subject matter) that is applicable only to you, if, even after being turned into a painting, the work is still readily identifiable as your creation, copyright infringement laws apply.
Regardless of whether you ultimately decide to pursue legal action or not, the first thing to do when you suspect copyright infringement is get a second opinion from an educated, but unbiased party, such as an attorney, or even an acquaintance.