Tallish, lanky Elf with (very) dirty blonde hair.  His clothes and armor were once quite posh, possibly of nobility, but long fallen into disrepair and uncleanliness.  Indeed, unclean is a fit description for him as he appears for all intents to be a homeless bum with a severe aversion to bathing.  His scent however is reminiscent of moonshine and woodlands, surprisingly pleasant if you like either.

[EDIT]  Of late (the last week) Jareth has been uncharacteristically clean and in the company of beautiful young woman, she is probably the reason for the cleanliness.  [/EDIT]

His constant companion is a sable polecat that answers to Akimbo, "Oops, I dropped my food", and "Where did my [shiny thing] go?"

Jareth is clad in a heavy leather Great Coat and heavy leather pants, the gilt all worn away, gems long plucked from their settings, colors faded and stained by who knows what, ground in dirt obscuring any markings.  He carries a hiking staff (jo staff length), wrapped in stained leather and linen strips, obscuring it's material and any designs.