There’s an image of Dr. Strange hidden on the cover of Pink Floyd's second album, A Saucerful Of Secrets. The fragments come from a page of Strange Tales (1967) #158, illustrated by Marie Severin.
The album cover’s composition looks much more complete to me when these images are pulled forward. It makes me wonder if the record company was nervous about legal issues and the images were burned out at the last minute, resulting in the awkward-looking empty spaces.
Designer Storm Thorgerson would later go on to design some of the most iconic album art of all time, but this was the first one he ever did. With the pop art movement in full swing, it’s possible he didn’t understand the difference between this and what Lichtenstein was doing.
(To be fair, there wasn’t actually much of a difference; they were both reproducing comic art without crediting the original artist. But in art circles, it was the act of reproducing comic panels at such a large size that magically transformed it into “high art.”)
Unfortunately, we may never know for sure if he originally meant for the images to be more prominent or or always intended for them to be a hidden easter egg. I don’t think he was ever asked about this specifically in any interview, and he passed away earlier this year.