Short answer: No. Long answer: Let's get to reading.
Today's music industry differs in a lot of ways from what it was in the 19th and 20th century. For one thing, studios are usually not all that picky about who they record as long as you've got the cash up front. Unlike the former years, artist's big and small can find representation from show promoters, social media, and word of mouth, and aren't exactly dependent on labels to get their name out there.
So what's the deal with the boys dressed to the nines with fad-style hairdos and matching costume to take the stage? And moreover, is holding a specific image central to a band's success?
Well, "the deal" as it were is that bands, especially serious bands, are performers- entertainers. Nobody wants to see Slash take the stage in sweat pants and a graphic tee. (Although if anyone could, it'd be him). While it wouldn't matter, because what we came for is the astonishingly cool tunes that come through that guy's fingers, the way you present yourself onstage is somewhat just as important as how you play.
In a word, yes. If you want to be serious about your performance, getting your band squared away with a specific style, at least for when you take the stage together, helps a hell of a lot on presentation, but no, it isn't just as important as talent.
Talent should always be the first thing you look for in a band. Not their level of tenacity, their history, their questionable commercial deal to turn the month's rent, and especially not the kind of style their sporting.
Although it doesn't hurt. Image is a big thing when you're a public figure. A good artist taking the stage should very much be representative as larger than life, or at least, above the norm for a short while. A great musician will be a great musician either way, but remembering these guys came to deliver a show should factor into whether or not we think of them as sell-outs just because they're trend-setting or following a current fad to endorse themselves and their latest works.