It's pretty common for people to bring in photo's or look through books at a barbershop so I don't see why celebrities would make a difference. I wouldn't mind asking for this one johnny depp hair cut once it's long enough.
I don't know about barbers but it is pretty common in salons. Many have stylebooks and magazines for the customers to flip through if they need ideas. Good stylists should let you know if the hair style in question is actually suited to you.
ALlright, sorry about the delay. She said that in her experience it is usually women that ask that however she sees no problem as long as it is a realistic question, e.g. if you have typical Scandinavian wispy flat hair don't ask for an afro