There is next to no restriction with this breed of Steampunk. In fact, since 2007, the 8th of December has become known as “Pretend to be a Time Traveller Day”. Any era, or a mix of these eras is completely acceptable in this genre. In Steampunk, the most memorable depiction of a Time Traveller comes from Wells' novel The Time Machine, or it's contemporary geek-culture equivalent, Doctor Who. Both main characters from the novel and the film are unnamed, and involve the story of a character who travels through time in search of adventure and companionship. With a little research, there is endless character material for a Steampunk who wants a few conversation pieces. The Time Traveller is the ultimate social butterfly of the Steampunk world, able to converse and socially interact those of other genres and influences freely.
The Time Traveller -
Over: Steampunk Airship Pirate by Drackinn http://drackinn.deviantart.com/
Top: Starboys Dancers by the Time Machine at Steamfest.
Below: Alchemichal Caberet.