Everyone has a gimmick. The image that a band or artist or whatever displays is always a factor.
I saw Arcade Fire on SNL, they were dressed up in uniforms with flashing lights on them. Maybe not as outlandish as a meat costume, but at some point, these people had to sit down and discuss putting on these (gimmicky) outfits. I'm using them as an example because they seem to be a band that people look at as ultra "genuine" or something. But you can look at almost anyone and find similar aspects.
Where do you draw the line between "gimmicky" and "showmanship"?
People like Gaga and Madonna (Not sure why you are trying to separate the two, Gaga might just be a degree more silly than Madonna, but Madonna was faaaar more controversial at times) are simply more straight-forward. In some ways...you might even consider Gaga more honest than a lot of people. Everyone has pretense, not many are as open and transparent about their pretense as Gaga is. And this is coming from someone that isn't really much of a fan, I think her music is pretty generic but I'm not gonna hate her because of her clothes.
