Photographing animals can be tricky. If you have existing photographs you can email them to me to see if they are of good enough quality. If the animal has passed, then I will work with what you have, but no guarantees are given for poor quality photographs. I do require actual photographs to paint from and don't do jpegs, nor do I print them here to use. The photos should be at least 5 x 7", though larger sizes are usually not necessary.
The best way to photograph your animal is to first, have help. With digital cameras more is sometimes better as there are more photos to choose from. If you are photographing a dog and they have a sit stay, that is ideal, as you can get farther away, have your help get the dog's attention and then you can click away. It is best to give small treats for all the good work your dog does, and helps with keeping an alert attitude for the photos. Time of day also is important, as early morning or later afternoon, photographs can be more dramatic for shadows, though you don't want the have too strong shadows so I can't see detail in them. Using a flash helps with giving detail in the shadows.
If your dog doesn't stay, then having him on leash so your help can control the dog will make taking the photos easier. Also having the dog look different ways, sideways, or a 3/4 angle can work well, as opposed to just shooting the dog looking straight forward. A 3rd person is ideal and can go far behind you to make funny sounds or squeak a toy. Those sometimes are the best photos because the dog is usually very animated and "posey".
Horses are a very difficult subject, but it's best to have at least one other person, if not two to help. Angle on head, being too high or too low can give bad photos. Having a piece of tin foil, plastic bag or bottle with rocks in it can get a horse's attention. Do the best you can. Wished I was of more help!
Cats probably are best taken when they want to have their photograph taken. They also can be difficult, so I recommend taking as many as you can. One of my favorite cat portraits was of two cats taken outside on a brick wall. They were separate in the photos but I was able to incorporate them together in their garden & added a butterfly that wasn't there. So, a cat in it's environment is a very nice way to go.
With photographing your loved pets, I cannot stress enough to get photographs of them even if you have no intention of getting a portrait done, or have to wait 'til the funds are available. Animals leave us all too soon and there is nothing worse than not having good photographs of our loved animals.