Jennifer Aniston & Justin Theroux Wedding … A Little Chill, A Little Rage

Jennifer Aniston's wedding dress set the tone for her big night ... casual and easy in which to dance.

Aniston shunned a traditional wedding dress ... opting for flowy, white and summery. Some guests showed up in jeans since they thought they were coming to Justin Theroux’s 44th birthday party.

We're told the couple made the big reveal once all guests arrived ... and Jen apologized for tricking everyone.

As for the reception … we’re told the couple's table was family only. Howard Stern and Robert Downey Jr. gave toasts, while Sia performed and sang happy birthday to Justin.

The party then kicked into high gear ... Samantha Ronson DJ'd late into the night -- some guests stayed until 4 AM.

The hangover couldn't have been terrible ... the newlyweds were spotted hopping on a private jet Thursday morning, presumably to honeymoon.