I believe the shape is supposed to be evocative of wings. Sam is the Falcon and he wore the EXO-7 Falcon suit. However, earlier in the episode Walker had ripped the wings off of the suit breaking it. Sam then leaves the suit with Torres. So he now has no wings. Later in the episode Bucky calls in a favour with the Wakandans and goes to Sam with the crate.
Bucky: Just dropping this off. You can sign for it and I'll go. I called in a favor from the Wakandans.
The Falcon and the Winter Soldier, Season 1 Episode 5, “Truth”
Now the whole episode has essentially been dedicated to character development on all fronts but primarily focused on Sam. Sam’s development has been on whether or not he will take on the mantle as the new Captain America. He eventually decides to. Now given Sam already has the shield, the box is unlikely to contain a new one. So, the likelihood is that it is a new suit, probably with integrated wings. Given the design on the front is reminiscent of stylised wings: two wing-like shapes extend from a central structure.
Given that the case did in fact contain a new Captain America suit with wings this is almost certainly what it was meant to be. We’ll likely know for sure in the Art Of book as well when that releases.
Just to be as complete as possible, whilst it could just be generic Wakandan shapes, we do see the box that Bucky is given with his new arm in it from Avengers: Infinity War. This does not have the same design.
It also doesn’t seem to match the design on Steve’s Wakandan shields, also seen in Avengers: Infinity War.