Anybody recognize this dog-herding-sheep picture?

I googled the crap out of several keyword phrases to no avail.

Is there any chance she took that with a film camera? If so you could have the prepress department of a large format printing company scan the photo at a very high resolution for you. That would give you a working chance of reproducing it poster size. The fee would be worth it to get it done for grandma.

I'm not sure how well that would work from a digital print. Maybe.

 

It's not that old, those look to be a pair of reasonably modern vehicles in the background.

You should be able to use what you have. If you're worried about black helicopters and the copyright police rappelling down ropes into your home to clap you in irons and carry you off into the night disabuse your mind. It's not going to happen.

You might brighten it up a bit, it's a rather dismal image color-wise. If nothing else you can pass it through something like Alien Skin Snap Art and make an oil painting or something out of it. It's a good stunt to pull on crappy images. Granny might fancy that. She'd have the only one like it on the planet.