I am just a shopkeeper. Sometimes I tend bar, but only on certain nights.
I have balding hair, and a fat belly. I keep my attire simple... perhaps a workman's robe, or typical shopkeepers wear. Cloth clothes for this fella - let those who are "warriors" worry about armor and such things! Those just get in the way of my business!
When the time of course is right, and the 'shadows' all line up just right... and their back is to me. In one fell shot, oops - they forgot! Shopkeeper's need lovin too! The next sound we hear, is that of a lifeless 'thump' of bones on hollow wood. Then of course, this simple shopkeeper will just clean up the mess.
I guess my point is that no assassin would ever actually admit such a thing. They would find themselves locked up too fast!
There are two schools of thought for public attire;
1. Common, so common it comforts the onlooker because of how 'normal' you appear.
2. COMPLETELY outlandish; whereby the onlooker is so dazzled at your clownish appearance they are distracted, and thus overlook your clandestine purposes.
I guess of course perhaps being a loudmouth moron that wears a title of 'assassin' and hangs out in a mmo... bragging about childish exploits, may make that person feel rather 'larger' than they actually are.
I guess such amatuer displays will distract the onlooker, make it all that much easier for the true professional to do their work