The Crown
At the beginning of the play, it is reported by Casca that Antony offered Caesar a crown three times, but Caesar refused. Despite his rejections of the crown, Casca notes that Caesar seemed to want to accept it anyway, suggesting that he (Casca) does not see Caesar's refusal as genuine. The crown therefore comes to symbolize Caesar's ambition and desire for absolute power, even if he makes a show of rejecting the notion in order to stir the energy of the crowd.
Wives
Caesar's wife Calpurnia and Brutus's wife Portia, while characters in their own right, serve a symbolic purpose in the play as well. Calpurnia and Portia represent private or domestic life, as they are only present within the confines of the home. They highlight a stark contrast between the anxiety and secrecy inherent to the male-dominated world of the Roman government, as they pursue honest conversation with their husbands. Portia and Brutus have a particularly loyal and loving relationship, one so strong that Portia injures herself to prove her commitment and eventually commits suicide once Brutus's own fate starts to sour.
Poets
Poets, teachers, and other learned people are a recurring motif in the play, largely in terms of how fervently they are ignored by other characters. The clearest example of this motif is Cinna, who is literally killed by an angry crowd for "bad verses." At the beginning of the play, Caesar is warned by the rhetoric teacher Artemidorus about the impending danger to his life, but Caesar completely disregards his words. Poets and teachers therefore appear as wise, worthy, and valuable voices within the realm of politics, and the play suggests that these voices should be heeded by heads of state.
Omens
A central recurring motif in the play is omens, or harbingers of bad fortune. The first omen comes when the soothsayer tells Caesar to beware the Ides of March, which Caesar ignores. Then, reports come of bad weather and strange animal noises in the night. Finally, on the day Caesar is meant to travel to the senate (where he is assassinated), Calpurnia admits to having a dream about Romans washing their hands in Caesar's blood. What is notable about these omens, like the role of poets in the play, is that characters (namely, Caesar) rarely listen to them or take them seriously, thereby sealing their own demise through the stoking of their own ego.
North Star
In Act Three, Caesar compares himself to the north star, arguing that he is unassailable, infinite, and constant. For Caesar, the north star symbolizes his sense of strength and resiliency as the leader of Rome. For the audience and the senators, Caesar's announcement is painfully ironic, as his proclamations of constancy are met with his assassination just moments later.