Complex sentence: Marky Ramone was kicked out of the band during the production of the album, and he is missing from the cover art. He was eventually replaced by Ritchie Ramone, who is lurking almost invisibly behind the window on the front cover.
Split into simpler sentences: Marky Ramone was kicked out of the band during the production of the album. He is lurking almost invisibly behind the window on the front cover.