I came across this exact image a few months ago and came to the same conclusion, that it was artists and architects aiming to bring to life the psychedelic experience, through religious architecture.
I made a small collection of similar imagery here
Where to cop this t-shirt? I know it’s an old Sebastian record, but I can’t find anywhere that officially sells this t-shirt in this light blue colour. There’s unofficial copies on white from Redbubble, is that my only option? Or I could try and print one myself.