why do people always assume songs only have one narrowly defined meaning? My theory is that the song is both about LSD and inspired by the picture... It's not a coincidence that the line "Lucy in the Sky with Diamonds" has the letters L-S-D. Given that the song was released in 1967 and Lennon and others first used LSD in 1965, and given that the lyrics of the song go well beyond describing a simple picture and are loaded with what sounds like descriptions of psychedelic visuals, I think it's pretty hard to argue that Hoffman's problem child wasn't in mind when this song was written.

Anyway, you're probably right; DMT is among the most visually intense psychoactive substances out there. LSD could lead to this sort of experience, too, although many feel that any visuals an LSD trip may include are minor sidenotes at best to the more abstract elements of the psychedelic state.