Harry is not meant to look like comic Goblin 100%.
The new pic - he looks enough like Goblin imo.
And the point is, he's not portraying THE Green Goblin.
He's not mutating into a green monster with long ears...he's physically degenerating, hence his grotesque appearance.
He's not interested in theatrical costumes with cloaks and long caps...
The costume he's wearing is designed to give him enhanced strength, because he has no powers, unlike the comics.
Harry's not meant to be seen as comics Goblin. Because he's not. He's loosely inspired by the concept.
There's a logic and reason behind his creation into this villain he becomes.
Norman, however. He might mutate into the monster Goblin, unlike Harry's degeneration into a grotesque and deathly looking thing.
Norman might end up creating a costume based on Harry's look after taking the serum.
Might be complete with mask and cap, and I'm guessing that might be the case, because it would make sense like that.