Three sketches of the slate spotted on the side of a building have been photographed and uploaded to a Facebook account belonging to a user named SurfEvangelist.
Microsoft has refused to officially confirm that it sanctioned the campaign, but the computing giant has adopted similar tactics in the past.
Street art promotions were used to support the launch of MSN in 2002 and the unveiling of Windows Phone 7 five years later. Both endeavours sparked an angry response from city officials.
Microsoft's Surface, touted as a competitor for the iPad, will launch in both Windows 8 Pro and Windows 8 RT models, with specs varying between the two devices.
However, both editions will feature 10.6-inch ClearType HD displays, multi-touch keyboards that double as a magnetically attached cover, and front and rear cameras.
Surface will be released on October 26.