What is the symbology of a crow tattoo?

Hi. I have to say that most tattoos take on a personal meaning... a large part of their meaning is cultural. Crows/ravens are respected as rather negative to some and very positive to others. I, personally, have two ravens tattooed on my shoulder; they represent Hugen and Munen - they are the birds which perched upon Odin's shoulders in Norse tales. Their names translate into "thought" and "memory." Take the bird you want and combine it with another image... give it some meaning and make it your own. Nobody can tell you it means something other than the purpose you have given it. I hope I helped at least a little.