To stay on brief, or not to stay on brief, that is the question!
Why do briefs exist?
My personal experience of larps and brief is as such: A game has a look and feel it wants to follow - kit guides, uniforms, colours for certain things, culture briefs - all of these things contribute to the overall design to the game and what the designer wants to achieve.
A free and open brief can cause a lot of contention and slight pandemonium for organisers of smaller games.
Briefs are vital. Without them, the game can become flooded with micro-cultures, stray storylines and many, many clashing aesthetics which, if the game is aiming for something in particular, could prove very frustrating to the designers.
It dilutes content and you may even find yourself wondering why your character is even there in the first place or even why they would care about the goings on around them.
Even huge games such as Empire, Curious Pastimes and Lorien Trust have briefs about the game's races/factions written to inform and encourage players to adhere to a basic set rules which help the game team keep things together.
So, if you have an awesome concept which is possibly a bit out of the box, great! But here's a couple of things to think about before you get too invested in it:
1) Have you read the fluff?
Game organisers spend a lot of time writing engaging back story and constructing the world. More often than not, the content of which will be designed the way it is on purpose.
Erda, for example, has cultures designed in specific ways for specific reasons which contribute to the overall storyline and how politics function in the game. The world of Erda is vast and diverse, but the cultures still have aesthetic, religious and cultural rules which make them unique and stop them from blending too much into one and other.
2) Can you see the character idea integrating with the world set out in the fluff?
If you can see your idea integrating with one idea or another, fab, you should probably make sure you aim for something similar to the rules set out in that culture, aesthetically, religiously and culturally.
3) If the character idea won't integrate well into something already existing, why so? Do you think that it'd still be a good idea to go ahead with it?
A badly integrating character idea can do a lot of harm to the level of enjoyment a player can get out of a game. If you have an atheistic character in a highly religious world/cult for example, you're very likely to either be lynched, shunned or killed very quickly. That's all your hard work and effort on costume scuppered before you even had time to enjoy yourself.
4) What would you be losing if you integrated the idea a little more into the existing fluff?
Is there really anything?
5) What would you gain from integrating?
Better cohesion with players cultivates a better sense of involvement. You'll have better chances at gathering plot and create better relationships and opportunities for your character. It also means that organisers don't have to break or bend world rules for concepts which may not work well with the overall game.
Coherent looks are the best looks.
Naturally, it all varies from game to game. Many game organisers are more than happy to help you integrate an idea into the game, but please don't expect already established things to be re-written, even if it is a diverse world or has many things unsaid or unexplained yet.
Like I've already said, there are often good reasons which need respecting.
After all, that's what a game is: a set of rules which we all, as players and organisers, are trusting people to play by.