As I've been playing 3.5 and pathfinder in a combination for over a decade, to me it has always seemed that Shadowdancer's name refers to their ability to teleport from a shadow to another. Having a shadow as a companion is certainly another iconic thing to them. The 3.5 version of Shadowdancer is rather weak and also quite boring. I'd suggest to take a look at the
Pathfinder's version for more inspiration. Maybe there's something that could be used as a guideline.
(If you're wondering what that page is, it's Pathfinder's official SRD.)