The photo of this stunning horse is licensed CC by-sa: https://commons.wikimedia.org/wiki/File:Mangalarga_Marchador.jpg
He’s owned by Quitumba Ranch in Brazil. That Wikipedia page says author = Fábio Vidigal, so maybe that’s the name of the photographer. Don’t you love that neck?
Oh, this is gouache, except for a wash of transparent blue over the ‘sky’.