I'm completely for cosplaying as OCs. I make up lots of characters and have dressed up as one before and it went over extremely well. It is by far not my best cosplay-construction, materials, sewing wise-but it was all made by me, and I had a lot of fun being that character. I'm now working on my next original cosplay and hope it gets good attention, but if not, I still love it! I've done many already established characters and only got a lot of attention for my first cosplay as the others I've done hardly anyone hears about, or in my L case, too many people cosplay.
To me, OC cosplaying is not really about getting attention but dressing up as a character you yourself have created and loved. It's really all about fun and heart which to me, all types of art is meant to be about, and I (personally) do consider cosplaying a type of art.
Cosplays in Progress:
Ohnah the Shadow (original character) (60% complete) (Progress currently on hold)
AWA: Might be attending.