I've always loved the cover for the Patti Smith album Horses. 
It's a really great portrait with the artist staring out defiantly. Wearing a white shirt from the salvation army, black jeans and a black ribbon, she strikes a dramatic pose. I didn't realise quite how perfect the shot was until I started working on it. 

I certainly haven't done it justice and it definitely loses something from the original, but it captures an attitude I'd like to reflect in my work moving forward, and for that reason it was worth doing.