Depends on which body you're talking about. Assuming, of course, that you're talking about the only one you all have ever really interacted with..
Green eyes. Always green eyes. It's the first thing anyone notices, no matter how he's dressed or what he looks like. No matter the race or gender or form he takes, it always has those green eyes that glow in darkness. This is a identifying feature, a trademark, a leitmotif. If it doesn't have green eyes, it's not properly him.
A slim young man with those green eyes and usually with some discrete brown hair. He likes wearing formal clothing of a neo-victorian make. He wants to look rather spiffy. No tuxedos though, as they make him look like a penguin. His clothes are usually in a set of bright colors or pastels, and there are usually some arcane markings subtly worked into them- on lapels and buttons and along edges of coats.
His shadow is alive, of course, but it's far more mellow than it ever was before.
It can be safely assumed he has a sword somewhere. In hammerspace if nowhere else.
Is this enough to work on?
“She'd become a governess. It was one of the few jobs a known lady could do. And she'd taken to it well. She'd sworn that if she did indeed ever find herself dancing on rooftops with chimney sweeps she'd beat herself to death with her own umbrella.”
― Hogfather