It is a Cod-fish. Sort of like a cod-piece, but ...a fish. That thing he is carrying is a gigantic Khopesh, an accessory that makes an Ægyptian / Canaanite fashion statement.
Well, I wasn't going to post it (mainly to keep the pressure of doing it off), but I've put a link below.
He's very lithe - I would picture him as a warrior subspecies from the drowned temple city, or blessed by Tzunki. You would have no trouble selling that sculpt. Beefing up the concept wouldn't be too difficult, but for me a slann is more about contemplation than action. He might just melt my face off for saying it, but he is more likely to use a casual gesture than a big Kame Hame Ha.
I found the original link: http://xholankha.deviantart.com/art/Sketchie-Thor-438152786 sadly the content is gone, perhaps you could find an archived copy on https://archive.org/index.php
Thanks N810, I found his DA page, but was trying to dig around for a cached version of it. Tried wayback, but surprisingly it only had one image (an ad).
I poked around a bit at home, I got a bit further and could see a bunch other pics, but sadly not that one. (yea it was only one cash )
I did find the guy's patreon and tumblr accounts through reverse eye, but no more joy unfortunately (although I don't have a tumblr account), I also found this too (which he also did...which is also too small and has an interesting head design).