Plain sight/unmasked/gentlemen shaco skin
A Shaco skin in his true identity. I think it would be extremely unsettling if we find out that when he's not slashing throats in a jester costume; he appears to be a completely normal or even nice person. He should be some high class nobility. Someone who is extremely charming and charismatic. He should appear very laid back, someone who can easily make you lower your guard.
His clothing should be late 1800s to early 1900s. Some ideas on the style of character his appearance should emulate.
http://fc06.deviantart.net/fs71/f/2011/321/c/4/profile_picture_by_firo__prochainezo-d4gimu9.jpg
http://images6.fanpop.com/image/photos/34500000/Oz-Vessalius-oz-vessalius-34569943-225-350.jpg
(The last two images are white rabbit and mad hatter from the Pandora Hearts version of Alice in Wonderland. Hatter might be a bit too obvious about the fact that he hates everyone. Oz (the rabbit), while genuinely nice still gets pretty terrifying at times. )
Also, I think using the ult (halucinate) should cause him and his clone to revert to the normal jester skin for the duration of the active. I think it would really drive home the fact that they are the same person.
