Imagery of royalty runs throughout the novel. Faulkner compares Sutpen's "design" to the attitude of a king, suggesting his outsized sense of entitlement. Sutpen clearly seeks to run Sutpen's Hundred like a grand empire of which he is the unquestioned head. As Miss Rosa bitterly points out, he named his plantation "Sutpen's Hundred as if it had been a King's grant in unbroken perpetuity from his great grandfather" (1.11). The irony is that Sutpen has no past and is anything but a king in terms of lineage and history. He came from nowhere but assumed the attitude of a king. This arrogance is offensive to the people of Jefferson, who resent that Sutpen lives in "baronial splendor" (2.8).
In an interview, Faulkner uses the language of royal privilege in describing Sutpen: "The important thing to him was he should establish a line of dukes, you see. He was going to create a dukedom. He'd have to have a male descendent. He would have to establish a dukedom which would be his revenge on the white [sic] Virginian who told him [through the black butler] to go to the back door" (source). Even the author sees Sutpen in terms of royalty, so that tells us we should probably pay attention.