I recently received an email from a Julia Woods in the UK (Buckinghamshire) asking permission to use my "7 cats in a bed" photo on a brochure for a Feliway product. Since I was not familiar with the product, I did some checking online and with my Veterinarian's office and was assured that they were familiar with it, it was a good product, and they even carried it at their clinic.
So I sent off the picture (and these 2 others) to Julia explaining why I hesitated, but that I was happy to let them use my pictures as long as they realized that I wasn't endorsing the product because I myself have never used it. As you can see from my photos, there was never a need. My cats get along fine. But hey, if it helps other cats to get along...