...It was mentioned in this article
at TrekMovie that it is indeed a fabric pattern...
As TrekMovie’s closer look at the new poster reveals (above), the colored uniform blouses have small ‘delta shield’ emblems woven into the fabric (this is most apparent on Saldana’s)
That just means: "Hey, we looked at the poster and saw a delta pattern."
That is no more authoritative than anyone else looking at the poster.
I should point out, though, that I'm happy if this adds more depth to the uniforms so that they look great on a 40' screen or in high-def -- I'm not certainly against the idea, just a bit dubious at this point that we're not just seeing some creative license in the poster art.