Venom's Design
Spider-Man is not in Venom and the reason is to avoid including the latter in the Marvel Cinematic Universe and confusing fans. But that presented a problem. Venom's entire design is based on Spider-Man because the symbiote originally bonded with Peter Parker (the black suit) before it met Eddie Brock. 

The Venom filmmakers weren't using that story so there's no real reason Venom should look like Spider-Man in the film. That's why the movie Venom doesn't have a big white spider on his chest. However, the movie still had to keep the character's original design intact for fans. So Venom has white veins to replace the spider and he still has Spider-Man's eyes, which makes no sense, but perhaps foreshadows a future movie where both Spider-Man and Venom come together... as it should be.