There are some great shops in Liverpool from the low to the high brow.... Cricket is probably the most famous! check out their home page. The funny thing about Cricket is that its laid out a bit like a jumble sale - but it's filled with amazing clothes that only the footballers wives can afford. What tends to happen there though is that the local ladies go to Cricket, find what they like and then go and buy the high street versions.
* "Grand Central" formerly Quiggins. Quiggins was one of the former landmarks of Liverpool, similar to Afleks Palace in Manchester as a collection of independent and alternative store holders. It was a meeting place for primarily teenagers and adults who were after cool 2nd hand, vintage, trinkets or traditionally non-mainstream things. The building was located near the Bluecoat arts centre but was demolished to make way for the Liverpool One development which has built over huge sections of the city as was pre-2000, A history of quiggins can be found at:
Grand Central is the reincarnation of Quiggins, with friendly people who will help you find or be able to direct you to what you're looking for, from the everyday item to the feather boa and party outfit.
* Heritage Market (set up by the same fella who started camden market in London) - just jump in a taxi and ask the driver to take you there