What would be polite is to link the website if you don't know who the photo was taken by (copy and paste).
The first photo in that post is in fact mine.
But this goes for ALL photos you take from anywhere (and videos) always link the source above or below the photo directly and if you know who owns it then give them credit else things can turn bad fast cause I know I am becoming a lot more protective of my work which also means I will hunt down those that take my images/videos without my permission and punish "heavily" (specifically if their profiting somehow, then I will show no mercy...).
Food for thought.