On Wednesday, Valve took a page out of Apple’s playbook and distributed teaser images that hint pretty strongly at its upcoming plans, namely, that at least some, if not all, of its games are headed to the Mac. With Game Developers Conference planned for next week in San Francisco, it seems likely that the publisher will have more to say then.

Various web sites received different images accompanied by this explanation: “In anticipation of an upcoming announcement from Valve.” Mac Rumors, for example, received one showing Half-Life character Gordon Freeman with a partially obscured Apple logo on his chest, while MacNN received one mimicking Apple’s “I’m a PC and I’m a Mac” ads and Macworld was the recipient of a recreation of Apple’s famous 1984 commercial, starring Alyx Vance from Half-Life 2.

Rock, Paper, Shotgun received the strongest piece of evidence, which seemed to confirm that, at the very least, Steam is headed to the Mac. The image is a parody of Apple’s original Macintosh print ad, complete with text that explains, in part: “In the olden days, people had to go to stores to buy games. It was awful.”

Given the fact that Shacknews received an image that references Team Fortress 2 in an iPod ad parody, it’s possible that Valve is going to bring its games to the iPhone too, or even bypass the Mac in favor of the App Store. Valve sells games other than its own on Steam, so it could simply add Mac versions of the relevant titles.

However, if Valve does publish at least some of its games on the Mac, that would be a marked turnaround from October 2007, when Valve managing director Gabe Newell said in an interview that the lack of his company’s games on the Mac was Apple’s fault. According to Inside Mac Games, though, the real problem was “Valve’s insistence that anyone who wanted to port Half-Life 2 to the Mac had to advance $1 million to Valve.” Whatever the real reason was, the perception in the gaming community was that Valve had little interest in bringing games to the Mac.