I've cosplayed an original character, but it was for a type of costume day in high school... I find that the best reactions from OCs are when they are something sensical to people. For example, what I cosplayed was nothing more than an OC from a magic-like victorian era. It was well received because I just looked like a victorian gentleman.
If you get something very eccentric, chances are it'll confuse people what it is from. If you can fit it into things like "cowboy", "angel", "vampire" you can usually get better responses from people because they can approach on that basis alone.
Regardless, do whatever you wish. There will always be a totally unique satisfaction to cosplaying something you put your heart and soul into rather than just a character you're a fan of.