It's page 15 because that slideshow is showcasing the '04 DS pilot's script (and for some odd reason the scenes aren't numbered in it, so we had to go with page numbers).
But when it comes to the April background for the '91 DS, I'm not sure which capture you're referring to. But whichever it is, the character isn't Prof. Stokes because 1) there is no Prof. Stokes in the '91 series because they sort of merged the characters of Stokes and Dr. Woodard into a character named Prof. Woodard, but 2) even he isn't in the April background. So could you please be a bit more specific as to which capture you're referring to? And then I'll be very happy to tell you who it is.