First I agree with JR
Next I have a few suggestions myself
Looking at the montages they look great but the Fellowship of the Rings , the images seem too high, so I have an idea. Imaging your brown edging goes all the way around, then limit your character images to go within that imaginary rectangle, of course leave the bits that over lap (swords, staffs and so on
Like so, (Top left and right images altered.
Also the tag line, (One Ring to Rule them All and so on...) personally I think should be in the same place on all the covers, it will make them a bit more consistent.
Hope you don't mind me making a few suggestions
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