well....
in terms of rock bars in Newcastle there are at least 4 good ones i can think of, like trillion's, bottle of fosters, £1-50, buy one get one free! hurrah!
In terms of gigs, there is the metroradio arena where quite a lot of big names play IF they ever step outside London, Birmingham, Mancester and Glasgow when the tour the UK in a huge number of 4 cities. But yes, there are a lot of big names who come to Newcastle although i should warn you, there is a lot of pop!!
As far as smaller venues go, there are the 2 newcastle universities' Student Unions and they attract a lot of quality rock and indie who might not sell 1000000000 seats, but are still in demand and in the charts. There are also your usual giggy pubs where the local scene thrives. On top of ALL that, theres the city hall where people like clapton and sting right through to jamie cullem play.
hope that helps
marc