Sadly you can't play Overwatch right now, even if you're in the closed beta, which may not be back until sometime in February. But, to help with the withdrawal symptoms, what you can still do is dress up like the fine men, women, androids, and anthropomorphic simians that comprise the team-based shooter's cast. And thanks to the official Overwatch Hero reference kits Blizzard unleashed yesterday, you can do so pretty darn accurately.
Some of these costumes are awfully complex and so your mileage may vary, figuratively speaking, depending on your cosplay skills and experience. Roadhog, for instance, is basically a gas mask and a gut, while Pharah wears an entire suit of outsized armor, capped off with a beak-like helmet. But I think the assumption here is that prospective players of the cos will already have a handle on the basics of costume creation, and that these guides are all about filling in the details with specifics on colors (Soldier 76's visor glows a warm #f94c18) and up-close looks at the accessories, like Symmetra's cybernetic arm or McCree's hat and belt.
The guide covers all 21 of the Overwatch Heroes that have been revealed so far, each in its own separate PDF file. Get 'em all at Battle.net.