Voici un article en anglais sur la question sur le site de TOR :

Extrait :
"What is steampunk?
In three short words, steampunk is Victorian science fiction. Here “Victorian” is not meant to indicate a specific culture, but rather references a time period and an aesthetic: the industrialized 19th century. Historically, this period saw the development of many key aspects of the modern world (mechanized manufacturing, extensive urbanization, telecommunications, office life and mass-transit), and steampunk uses this existing technology and structure to imagine an even more advanced 19th century, often complete with Victorian-inspired wonders like steam-powered aircraft and mechanical computers."

et

"Steampunk sounds great! Where’s an easy place to start?
The basic rule of thumb for steampunk is “start period and then add.” One of steampunk’s great advantages is that the period it is inspired by, the Victorian era, saw the invention of photography and cinematic film. These in turn allowed for a visual record of people from all different classes, cultures and backgrounds, providing an unprecedented amount of reference material. People looking for fashion ideas, character inspirations or scenes to describe can find a wealth of starting points in the countless vintage photographs and film reels left over from the 19th century. All that remains is to add to or modify the depictions to taste, though it must be remembered that many aspects of a steampunk world and its people will likely remain virtually indistinguishable from the period that inspires them."