Time to bring Red Hot Chili Peppers into the mix.
-Tearjerker from One Hot Minute is about Kurt Cobain.
-Transcending from the same album about River Phoenix.
-Knock Me Down/My Lovely Man about their original guitarist Hillel Slovak.
-Eddie from their recent Return Of The Dream Canteen is about Eddie Van Halen
This is not including Venice Queen (By The Way)/Brendan's Death Song (I'm With You) about important people in the LA music scene who aren't recognized nationally. Dreams Of A Samurai from The Getaway while never officially confirmed, the lyrics to me heavily suggest it's about Scott Weiland.
This alone puts that silly notion that "all they do is sing about California" to bed.
Some others:
-Hollie Cook has a song called Ari Up which is a tribute to the lead singer of The Slits (who Hollie played with in a reformed version decades later)
-Donna The Buffalo have a song called Dr. King about MLK Jr.
-Temple Of The Dog's Say Hello 2 Heaven about Andy Wood