Yes, "suit yourself" is an idiom. It is often used to convey that someone is free to do as they please, even if the speaker disagrees with their choice. The phrase suggests a sense of indifference or resignation regarding the other person's decision. Essentially, it implies that the speaker will not intervene or argue further.
no an idiom would be like "it's raining cats and dogs"
Suit Yourself was created in 2005.
Don't take an action that will result in harm to yourself that you did not intend.
"smelling yourself" is slang (primarily African-American) for being conceited
The cast of Suit Yourself - 2008 includes: Maureen Mountcastle Tony Schnur
Suit Yourself - 2010 was released on: USA: 12 May 2010 (Underexposed Film Festival)
Doing a task by yourself without the aid of another.
To suit yourself is to do what pleases you. You use this phrase most often when someone has expressed a desire to do something you either would not do or have no wish to do.
You're a person whose popular or "in high demand".
If you "get your hands dirty" figuratively, you're willing to do the work yourself.
To poke your nose into is to insert yourself into someone else's business.
It originally came from cotton farming, and means to do an entire job by yourself.