It's really frustrating to see musicians that are good drown their talent in a gimmick.
According to Dictionary.com, a 'gimmick' is "an ingenious or novel device, scheme, or stratagem, especially one designed to attract attention or increase appeal."
If you're going to have a gimmick to draw attention to your band it has to be done right. Sure you can create and awesome theme and character to portray when you're creating your music, part of being a performer is putting on a great show. ie: The Locust, Gwar, Slipknot.
But copying other bands gimmicks is just poor form and will only make people talk shit about your band.
There are musicians in almost every scene that try to stand out. No one should want to be like some other musician, if you do you should be in a cover band. The best way to stand out is write good music and put on a good show.
Of course this is all my personal opinion. I've seen a lot of unsigned bands in my 12 years as a vocalist that have hidden behind masks and makeup. Some good, some bad and hardly any of them were unique with their gimmicks.
As Oscar Wilde said: