For those series about getting their cosplay right, Blizzard has released some references for key new characters, and they're quite useful.
These PDF files take apart the pieces of a character's garb, accessories, and in the case of Abathur, body parts, and show them separately so you can focus on getting each individual piece perfect. My hat's off to anyone who wants to cosplay this Abathur, by the way. Or pretty much anything of the Zerg persuasion. They are handsome sons of guns:
There are 10 guides at the moment, which can be found on the US Heroes of the Storm Blog, and follow the skins found in HOTS. Though apparently they're looking for a more permanent home. A "more permanent home" seems to me like a decent sign there will be many more of these to come, and that there will very likely be a home base for all Blizzard IP.
You can zoom right into these suckers and make out the details so you get the stitching just right on Jaina's Regalia threads, or artistically recreate Abathur's bulbous tumours to perfection.
And hey, you know what's funny? There seems to be a cosplay reference already out there for Overwatch, too. You can get those PDFs here, and dress up as characters in a game you haven't played yet.