Clean (un-ripped) jeans and a collard shirt meets the requirements. Most new-hires wear slacks and collard shirts through indoc, but they don't have to. There is absolutely no need to wear a tie.

ID picture is on day 1. Wear, or change into, the shirt you want on your ID.
Wings ceremony is at the end of the second week. Class and individual pictures are taken. Wear what you want for those pics.