Good concept art does more than depict the exact details of a fictional world, it depicts the emotions, the feel that the material is intended to evoke in the audience. Terrifying, horrifying, disgusting, awe-inspiring, enchanting, uplifting: the artist must do more than depict, they must evoke.
As in these pieces by Polish artist Grzegorz Rutkowski.
Here’s a gallery of Rutkowski’s best. More can be found on his DeviantArt page, At The Link!
(click to enlarge)