Hey I was at Khouls the other day and bought a JLA T-shirt. The thing is there are characters on it that I didnt ever think were members of the JLA. For example,

Robin(Dick Grayson)
Batgirl(Barbra)
Captian Marvel Junior
Wonder Girl(Donna Troy)

So could someone tell me if these characters were ever JLA members or they were just trying to fill the T-shirt with popular characters.

I can't answer that question but I will add that I also got that shirt as well as a Marvel shirt that was the cover of Secret Wars #1. Both are really cool.

Dick Grayson only ever served on the League as Nightwing, never as Robin.
Time Drake served on Young Justice as Robin.

Barbara Gordon served on the League as Oracle, never as Batgirl.
Cassandra Caine was a member of the Justice League Elite undercover as Kasumi.

Freddy has never served on the JLA. Billy was a member of the JLI, Mary a member of the Super Buddies.

Donna to the best of my knowledge has never served on the JLA. Diana, Artemis and Hippolyta have all assumed the title of Wonder Woman and served in the League. Cassie Sandsmark was Wonder Girl in Young Justice.

I think they were padding characters, might be wrong though you never know.