Sigil: City of Doors

Here's a question that's been nibbling the side of my brain for a while now. Asking for answers has been met with mixed results and I'm not entirely sure at all. Either you know for sure or you don't at all so here it is for all of you. Maybe someone can produce an answer that'll settle this matter on no uncertain terms...

Since Sigil supposedly is everywhere and nowhere, just how free am I to wing things? Can I make up different homeworlds outside the source material? If so, in what context? Just how crazy am I allowed to go when hammering together an origin story? At which point do the powers that be look me straight in the face, unflinching for several seconds before giving me five across the eyes?

Relax, my ideas aren't that awful but I'd like to know where the limit is before giving it a whirl.

There's one hard-and-fast rule regarding this which is laid out in the server rules. Your character cannot be from Earth.

Beyond this, the rules soften. Of course, any of the "canon" worlds from any of the D&D settings is acceptable. There is no rule against it, but it would be frowned upon and considered in poor taste if a character's background tied in to any fantasy or sci-fi setting from popular literature, i.e. being from "Middle-Earth", or something from The Wheel of Time, etc.

If you wish to use a prime world of your own creation in your character's background, there would be no rule against it. The only concern in this case would be falling within believability, and it being a world that works within the ruleset and common sense of the D&D rules. As a DM, I've already involved at least three unique Primes in the storylines I've run, amazingly enough all of which were primary elven worlds.

Three of my characters: Ceroy, Kefalee and Nam, are all from a world I made up myself, which I have since dubbed "Anyeh." A world of weirdness which I need to write down someday, but it's mine and my own.

Given that the setting allows for infinite worlds, so far I've had not one person speak out against it, at least not that I'm aware of. And it sort of gives the character a far more interesting and original flavour than using a prebuilt D&D world could ever do, even if it's just in the eyes of the character's player.

As Ceremorph mentioned, all DnD setting backgrounds are acceptable. However DnD is vast, there's a lot of room left for demiplanes and prime material planes for DMs to create for adventures. Same as dungeons and city layouts in smaller places are rarely designed to give DMs freedom.

Medieval-ish setting, possibly some steampunkish feel is basic guideline for the design. As in gunpowder might or might not exist, but it's about as reliable as blowing up to your face every second time. Technology is at best crude and unreliable, unless if it's mixed with magic.

And if you'll ever want something revolving around space traveling, then I suggest checking into Spelljammer setting <,<

Actually, I kinda wanted to ask if Dragonstar would be an option, though reading through the source books it wasn't entirely clear to me if it's just D20, or a DnD Campaign Setting.

Yeah dragonstar is a bit farfetched... spelljammer as mentioned is a cool space setting for D&D though :)

Gotcha ^_^ *is drooling over the Spelljammer construction site, and having a heart attack from the prices*

Well that pretty much answers it. My ideas were in the realm of the reasonable.
Now It's just a matter of acting on them...