Young Robert Baratheon concept art

I fashioned it a bit off of the leather Brigandine used in Winterfell

Antlers or anything protruding aren't actually very practical for helmets as they could catch blows and get the wearer disoriented as opposed to letting blows glance off, so I only put the tips on it.

I wanted him to look massive, so one of the first things I thought of was to give him this giant fur mantle. It's supposed to be the skin of a bear that he hunted himself, sort of a trophy like his antlers (we do know that he loves hunting).

I don't think the Stormlands are particularly cold for cloaks to be a thing, so I gave him a coat instead. I thought it matched the climate more like the Greyjoys' coats, being near the sea.

We got to see a bit of the Stormlands in Season 2, and I matched the shape of his gorget and pauldrons from the Stormland armor in the show, to establish that same-world feel.

In the show, we got to see some of the characters in "informal" war attire, like Robb during his uncle's funeral. I imagine this is how Robert would wear his tunic in war councils and such--he would not care enough to strap in his tunic.

I also took inspiration from Gendry's hammer in the show to establish a same-world feel, as in maybe Genrdy fashion his hammer from Robert's.

Alternative armor color schemes. (also the full antlers). Ultimately, I thought the plainer ones matched the contrast of the leather much better.

Even played with more Baratheon colors, (although inverted and resembling he Greyjoy house colors more)