By all means ask for more pictures. Also ask questions about the horse's medical history, any prior injuries or issues, also about their general temperament and demenor. And never take the info at face value.
Try to learn as much as you can about the feeding program and what the horse has been used for.
Go and see the horse in person, see where they live and what kind of condition they are TRULY in, look for glossy coat and kind, clear, bright eyes, solid feet and at least a spark of interest in life.
Take a trainer or your vet and go ride the horse you're interested in. You'll be able to feel (and your experienced trainer/vet will see) is there are any issues or problems.
Good luck!