I've always been partial to EMI CD covers.

I should add that my taste is abominable and ignorant, besides.

Great covers that I remember:

the superb black-and-white of Britten's recording of the War Requiem on
London (taken, I believe, from the Faber edition of the score); the cover
for John Eliot Gardner's recording of Britten's Spring Symphony on EMI; the
cover for Hickox's performance of VW's Sancta Civitas and Dona nobis pacem;
Menuhin's LP of Handel's Water Music; Willcocks's LP of VW's Hodie; Boult's
LP (2nd recording) of VW's Symphony No. 2 ("London") ECM's CD of Paert's
Miserere; ECM's CD of Rautavaara's Cantus Articus; Nonesuch's LP of Bolcom
and Morris doing Gershwin songs; Columbia's LP of Ormandy doing Hindemith's
Symphony "Mathis der Maler";

and so on.

Steve Schwartz