In addition to being a series regular on Providence, Peterson had the recurring role of Nate Westen, brother of lead character Michael Westen. He had leading roles in independent features Sedona (2011) and Hate Crime (2005). Other roles include the Hallmark Entertainment Movie of the Week: Hard Ground (2003), in which Peterson co-starred as Burt Reynolds's son, Joshua; Godzilla (1998) and Can't Hardly Wait (1998). Notable television guest star roles include such series as NCIS (2003) playing Thomas Pierce in Season 9, episode "Devil's Triangle", CSI: NY (2004) in the role of Henry Willens, in Season 4's episode of "Boo" and CSI: Crime Scene Investigation (2000) as Perry Haber in Season 7's "Burn Out" on CBS.
Seth started writing poetry in his teen years, then after a while lost interest. Shortly after he joined Twitter in March 2012, he was inspired to write and share his poetry again. On February 10, 2013, Seth became a published poet. His book, #Eclection, a top 20 bestseller on Amazon, contains 48 of his best poems written up to its publication date.