This is real, official art to promote a Fallout game. I found it on the site of the artist, link here.. The artist also did art for a promotional pinup calendar for Brotherhood Of Steel, but I noticed with a chuckle that on his resume PDF he says it was art for Fallout 2.
Yeah, I don’t really have a good PC at the time and I saw the game in a store one time and found out I can play it. Bought it and I liked it. Never thought about the other fallout games.