i think paul giblert actually does have a rockstar image... its definitely his own schtick but he developed a fun, quirky aesthetic which fits his playing style well and he's visually fun to watch. especially compared to someone who is more reserved and stoic on stage like an Eric Johnson or Mark Knopfler.
There are some guitarists who's image i think kind of falls flat - this is probably where Joe Bonamassa gets a lot of hate because we all remember when he used to dress like a generic 90s indie rocker and now he's got the bluesman outfit and sunglasses and it all just seems kind of fake. The reason why nobody criticizes Santana or Steve Vai or Yngwie for their visually outrageous aesthetic is because it seems totally genuine and true to who they are as a performer and not a costume.
Adam D is the first one who comes to mind for me. Berklee-trained musician and terrific producer. When he's not winning [EDIT] a showcase on the Price is Right, he's running around the stage in shorts and a cape.
Ironically, I think his anti-Rock Star image is pretty rock n' roll.
Subject of another current thread - Yusuf Islam (Cat Stevens). If you listen to his albums in chronological order you can almost hear his fascination with stardom fading away. He has an image as a man of peace and of humanitarian concerns, but not one as a rock star.
Mark Kozelek looked like some guy who works at a surf shop, but doesn't really surf, until around age 34/35, at which point he just suddenly transformed into someone's dad. I love his guitar playing (and songwriting, singing, etc...), though.
Also, Nels Cline looks like an accountant who "dresses the part (kind of)" for his bar band on the weekends. Again, though - love his playing.