This is my top 3 :
1) Live After Death (the colors are just gorgeous, this balance between the blue and the yellow is terrific, Derek has manage to reproduce in his own style the clear/obscure style of Rembrandt but with a very impressive bichromatic palette, and the Eddie is just amazing).
2) Powerslave (once again, the colors are just very nice, softer and very bright at the same time, the Pharaoh Eddie is beautiful and the details are extraordinary disseminated through the artwork and the booklet, plus this is the very first Maiden I've listened and I immediately felt in love with this masterpiece, that's why it's my 2nd favorite cover)
3) Somewhere In Time and Seventh Son Of A Seventh Son ex-aequo (the 1st one is marvellous with its huge amount of details and I love Blade Runner, the 2nd one is very relaxing with its equilibrium of pastel blue and white/yellow/red/green)