The last one actually does make sense to me. It has a dark fortress, the Crebain, Shelob and the Nazgul, with one of them drowning in a river. It's somewhat abstract, but a pretty sensible collection of the most evil beings in the book minus Sauron.

Now..the others...are...very artistic interpretations? Not half as mad as this Polish Silmarillion cover though. I've tried to understand the damn thing for years but...nothing.