The picture you see above is, supposedly, a leaked piece of concept art from Half-Life 2: Episode 3. It and 31 other images were leaked by site Valve Time, along with the assurance that they are, in fact, the real thing.
The images supposedly show various designs for Alyx Vance (including Alyx wearing Eli's green jacket and Harvard sweater), a man who looks a bit like Gordon Freeman in arctic-wear, the Resistance chopper (maybe) crashed in a snowy landscape and more.
We have absolutely no way of knowing if these pieces of art are legit, or part of some hoax/mistake, but, if it means anything, the site they came from is adament that they are real, posting:
"I just want to stress that we absolutely would not release these pictures if we didn't know for a fact they were real. They absolutely are. I mean, it's not like we're doing it to attract traffic to our site. We know our server can't cope with the load so we don't want massive influxes of traffic like this. You may have noticed we've been offline since!"
The images, if they are genuine, date back to 2008, so may represent art (or an entire game) that has been abandoned, so take this all with a huge grain of internet salt(tm). They could also be concept art from another game, or a student artist's portfolio. Or the work of a forger. Or a CIA plant. Or anything, really.
I put a request for comment or verification out to Valve, and when they get back to me, I'll let you know. Until I hear from them, I'm going to remain very skeptical, but your mileage may vary.
If you want to check out all the site, here's a Facebook page that has them all.