We're completely in the narrator's mind. That’s good, because we know almost nothing about his "outer" characteristics or his circumstances – what he’s wearing, where he’s from, what he looks like, even what his name is – and he spends most of the story by himself. From his thoughts, however, we know that he’s perhaps a little overconfident, that he gives a great value to being rational, that he looks down on superstition, that he has something against things which seem outdated, and that he is, in spite of himself, pretty easily freaked. That’s just about all we need, isn’t it?
We don’t know what the narrator looks like. Since he is the singular focus of the story, the "Physical Appearances" category doesn’t apply to him. On the other hand, for the three minor characters – the old custodians – we get the most information about their looks. For example, we get detailed descriptions of their pale eyes, decaying yellow teeth, and withered body parts. The two old men are even referred to by their physical deformities ("the man with the withered arm" and "the man with the shade"). For the narrator, the "spectral looks" (28) of the three custodians reflects their belonging to another age, where superstition reigned supreme. That they seem to belong to another age contrasts the custodians with the narrator, who looks youthful. Beyond that, though, the old custodians' looks don’t tell us much about their characters. Their other role is to add the atmosphere and ambience to the story.
The narrator’s decision to stay in the red room reveals some of his most important characteristics: he’s daring (or arrogant), aims to be rational, and disregards superstition, committed to taking a stand against it. Once he’s forced to walk the walk, however, his actions also reveal his weak nerves and nervous disposition. Even before he reaches the red room, it’s telling that he instinctively reaches for his revolver when he sees the Ganymede statue in the dark. We can tell that he’s getting jumpy. His nervous rhyming once he’s in the room, and his placement of a candle in the alcove, (because the shadows are getting to him), further testify to his fear. Then, there are those three screams when he really loses it. Admittedly, the narrator’s actions aren’t really so distinct from his thoughts, since he’s the narrator and usually tells us what he’s thinking or feeling about something as he does it.