I completely agree that the 'guitar' isn't the issue here at all. Slash would look just as cool with a PRS as he does with a Les Paul, the BC Rich and SG's he plays. Stick a SC594 in his hands in tobacco burst and it could easily be mistaken for a Gibson - until you see the neck/headstock. Orianthi looks cool playing on stage - whether she is playing alongside Michael Jackson or Alice Cooper or 'centre stage' with all eyes on her as a 'solo' artist. She and her PRS never looked out of place with Alice Cooper alongside other guitarists playing SG's, Firebirds or Fender basses.
The reason I mention Orianthi and not Mark Holcombe for example is that Orianthi has played with both Michael Jackson and Alice Cooper - two artists at different ends of the musical spectrum - as well as playing alongside Richie Sambora, Steve Vai, Billy Gibbons etc as well as performing on her own.
All you have to do is search 'Orianthi' on youtube and you will see a PRS being played - whether alongside other great artists with other great 'iconic' guitars - the video above is Orianthi with Billy Gibbons on an SG and Kenny Greenberg on a Gibson ES335 - her Gold top PRS doesn't look out of place at all. There is a LOT of video's of her live with a variety of different coloured PRS guitars and she looks cool as F... every time...
Cool is all about being comfortable with the instrument in your hands, confident to rock it and the ability to play the music, the brand of instrument is 'secondary'. People aren't looking at the instrument so much anyway, its the 'sound' it produces and the performance you put on. If you look like a dork on stage and mess up, it won't matter whether you have a PRS, vintage Les Paul, Strat or Tele - you won't look 'cool' regardless...
PRS guitars are versatile and can be used for all genres of music. The reason that Classic rock is associated with Les Pauls or Strats is because PRS weren't around in the 60's and 70's but Hendrix would look equally as cool with a Custom 24 as he did with his Fender Strat because he would have played the hell out of it with confidence....