Genres including photo editing, accounting, design & illustration, and animation & modelling have appeared on the service's Android application.
The ten additional categories, though currently empty, suggest that Valve is planning to extend its reach beyond gaming and take on the likes of Google Play and iTunes.
Valve is already opening up its service to the community by allowing them to vote which games it should distribute through the Steam Greenlight venture. It has been speculated that the firm could do the same with other software.
Steam's summer sale began last week and will run until July 22, offering discounts on thousands of titles, including Call of Duty: Modern Warfare 3 and Portal 2.
Valve is yet to confirm plans to bring non-gaming applications to Steam.