Snap Kick (get a free additional attack every round, but has to be an unarmed strike) and Superior Unarmed Strike (increases unarmed strike damage) are both really good for monks. Those feats are from Tome of Battle.
In fact, I encourage you to pick up that book and consider taking a level or two in a martial adept class. Many of the martial maneuvers evoke the flavor of a
crouching tiger, hidden dragon kind of monk.
That said, also consider Roundabout Kick (complete warrior), Flying Kick (complete warrior), Sun School (complete warrior tactical feat), and even Weapon Focus: Unarmed Strike.
Also take a good look at the grappling feats. Monks are scary when they're grappling, and can effectively remove weak targets (like most spellcasters) from the fight if they can establish a hold. Grappling and pinning also fit in with your "no killing" concept. So, yes, when you get the option, definitely choose Improved Grapple as a bonus feat.
Lastly, take a look at the style variants from Unearthed Arcana. Denying Stance and Passive Way, in particular, are pretty great.
http://www.systemreferencedocuments.org/35/sovelior_sage/unearthedCoreClass.html#monk
-z
PS: take a look at the various vow feats in Book of Righteous Deeds. They might not fit exactly, but you and a good DM can come up with something that fits. For example, Vow of Nonviolence restricts you from doing lethal damage to humanoids, and in return gives you +4 to the save DC of any non-damaging spells you cast. As written, that's useless to you--but maybe you could change it to +4 to the save DC of your Stunning Fist attacks.
