This might be a question for the admins, but I want your opinion as well:
Is a historic background from a fantasy world a big no no? (It probably is)
Next question, How far back can we go? Can it be past BC.... like 1100 BC or something?
One more question: Is the period of the dinosaurs completely out of the question?
I agree with Lionilde. Bear in mind that technically the age of the dinosaurs would be pre-history, hence pre-historic, as would say something from the stone age.
Good luck anyway.
I'd like to refer you to the following link about historical fiction and rules for writing it.
http://historicalnovelsociety.org/guides/defining-the-genre/defining-the-genre-what-are-the-rules-for-historical-fiction/
For me when it comes to historical fiction I keep the following in mind:
- Historical fiction presents a story that takes place during a notable period in history
- Historical fiction often presents events from the point of view of fictional characters of that time period.
- Artistic license is permitted in regard to presentation and subject matter, so long as it does not deviate in significant ways from established history.
The above points which can be found on a number of reputable websites probably answer your questions in relation to a fantasy world, this is not established history so could not be considered historical fiction.
About how far back you go again I would consider if you can call the setting established history. Much of what we know in relation to life during the time of dinosaurs for instance, is purely speculative based on assumptions made by palaeontologists I think the term used for this period "pre-historic" is an indicator of how we as writers should view it. I would not recommend a setting like this as it is more veering towards fantasy rather than fact.
Hope this helps!