Ah, innocence lost. What a great theme for a hard rock/metal band album cover. A smoking angel is a hilarious contradiction, working with the fallen angel idea on a number of different levels. Dio-era Black Sabbath devised of this idea first for their 1980 album, appropriately titled Heaven and Hell. This was the first album they released after Ozzy was booted from the band, and was a re-birth for them in a number of ways. With Dio's huge, epic pipes blowing Ozzy's nasal whine out of the water, the band speeds their trademark sludgy riffs into a faster, more energized metal that just kills it. Highly recommended.
It couldn't be a coincidence that Van Halen used this idea only four years later for their last David Lee Roth-era album. They do improve upon the concept with a fantastic smirking, impish Cupid-cherub illustration (a play on the classic Raphael painting), though the concept couldn't have been original after Sabbath used it. Regardless, 1984 sold 10 million copies, so most of you reading this knows this cover well, and have probably never seen the Sabbath one.

