Pomade (Motif)
Dapper Dan is Everett's hair product of choice. It's the only brand he will use and he goes to great lengths to get it. The Dapper Dan pomade that he uses in his hair becomes a symbol of Everett's vanity. This vanity and pride in his appearance is also Everett's weakness, in that the smell of the Dapper Dan allows the sheriff and other villains to follow the trail of the escapees; the police blood hounds are able to pick up the scent of the Dapper Dan. Everett's love of pomade and his brand loyalty to Dapper Dan also strikes a humorous note, because one hardly expects for a criminal escaped from a chain gang to be fussy about his hair product.
Baptism (Symbol)
As Delmar, Everett, and Pete are discussing what to do next in the middle of the woods, we see a group of people dressed in white heading to the river to be baptized. Delmar and Pete run into the water to be forgiven of their sins. Baptism is a religious symbol that precedes O Brother, Where Art Thou? and represents the way that Christians believe that being anointed in holy water by a priest will relieve people of their sins. Delmar and Pete accept the baptism in order to redeem themselves of their crimes and sins, to cleanse themselves from the wrongs they have done.
Music (Motif)
Many films have soundtracks, but O Brother, Where Art Thou's is particularly evocative and the film features many instances of live music throughout. As the film opens, the men working on the chain gang are singing. Then later, the Christians on their way to the baptism sing together. Then, Peter, Delmar, Tommy, and Everett form the Soggy Bottom Boys, whose version of "Man of Constant Sorrow" becomes a huge hit and serves a pivotal role in the climax of the film. Additional instances of music are when the Sirens are singing "Go to Sleep You Little Baby" seductively to the boys, when Homer Stokes, dressed as the leader of the Ku Klux Klan sings a song, and when Everett's daughters sing at the rally for Homer Stokes.
The Odyssey (Allegory)
The entire premise of the film is based on Homer's Odyssey, and as such, the film as a whole has a touch of the allegorical. The journey the men take is not simply a personal journey, but one that stands in for the experience of all men, looking for redemption, second chances, and treasure. Because of its mythic quality, the characters in the film come to represent archetypes more than individuals. Everett represents pride and leadership. Pete represents loyalty and seriousness. Delmar represents gullibility and heart. Pappy is a king-like character, while Homer Stokes is a wicked villain. The Sirens represent the dangerous lure of seduction, and Penny represents jilted wives everywhere. O Brother, Where Art Thou? is a parable, an allegory for life itself, and while its spiritual lesson is ambiguous, it mirrors myths of yore.
Flood (Symbol)
Just before the boys are to be hanged, Everett uncharacteristically prays to a God he doesn't quite believe in. The film leaves it ambiguous as to whether the timing is coincidental or divine, but immediately after Everett prays for help, a great flood crashes down on them, and the Soggy Bottom Boys are saved from execution. No matter if the flood was sent by God or if it was just the result of an infrastructural ordinance, the giant wave represents a redemptive miracle, a sign of the power of the universe (whether that be natural or divine). It represents that some kind of energy is on Everett and the boys' side, and that they will be saved and redeemed from untimely deaths.