Yes, these are actual photos of Mei and the Kittenbus, which remains an exclusive addition to the Ghibli Museum in Mitaka, Japan. This comes from the terrific 2003 DVD documentary, Lasseter-San, Arigatou. This documentary was released only in Japan, and is a video diary of Hayao Miyazaki's 2002 visit to North America for the Disney release of Spirited Away. The entire enterprise was under the strict supervision of John Lasseter, who immediately became Miyazaki's champion Hollywood.
Miyazaki shared Mei and the Kittenbus with the Pixar staff on his visit, and this is where the screenshots come from. Lasseter-San, Arigatou is a terrific DVD, and should be seen by Ghibli and Pixar lovers alike. Consider this a real gem in your movie library; the odds of this being released outside of Japan is next to nil. Too bad for the rest of the world.
I do hope Miyazaki has a plan to protect his works after his death. You just know the powers that be will be pillaging his works for endless sequels and cheap knockoffs. It it were an American cartoon character, we'd already have at least a dozen Totoro videos. Perish the thought!