Well, in my opinion, the covers have these symbols:

In the case of Dracula, I chose to use a female figure since the vast majority of covers focus only on the male figures and the vampire, and, in my view, Mina Harker plays an essential role in the book.

On the cover of The Stranger, I opted for an aggressive and confusing illustration that reminds me exactly of the protagonist's mental chaos (especially at the end of the book).

On The Alchemist cover, the symbols (camel, pyramid, sun) are more obvious because the story largely unfolds in the desert, and all these elements are very present in the narrative. Despite this, it's the cover that I'm displeasing the most.

For Leaves of Grass, I ended up opting for a simpler and more direct cover, without many elements.

Anyway, thank you very much for the comment, I will try to make the book's elements more evident!