Stocking for a 90g

youre crazy man! my yellow belly blue is too big for my 120 alone! shes like a little bigger than my hand, and i got big mitts, (esp for a scrawny guy). thats why im giving her to blaxx. really i feel bad for any distace swimmers that dont have at least 6' of space to bolt across the tank. not trying to ostracise here, just voicing my experienced opinion. although i agree that when theyre small it doesnt seem to be hard on them, but i have been surprised how fast tangs grow. 3 years go by faster than ive ever imagine. 
on the chevron tang, they also get real big, but most of all they are just all black and ugly when they go into their adult morph color. now if that doesnt sound like a anthropogenic perversion!
i do have to say tho ive never met a shy tang! my yellow belly blue is boysterous and my purple tang is an excellent diplomat, usually has to do some negotiating with the blue, but he holds his own.
my recommendations would include flameback pygmy angel, maybe a tang from the zebrasoma genus, any cirrihilabrus or halichoeres genus wrasse, or two, or one from the paracheilinus or pseudocheilinus genus. bangai cardinal, +1 on anthias, although a number of species can be difficult to acclimatize to the aquarium environment, esp with feeding. any number of gobies like a watchman/shrimp pair. although beware that multiple gobies and some blennies dont get along very well.
one observation is that a healthy and entertaining fish community is diversity and dispersing selections of fish throughout specific niche types. youve got sand oriented fish and/or cave rock dwelling fish (formifarian grazers), schooling groups (planktivores) to disperse the agression of larger open space cruisers (grazers and herbivores), pest control grazers like a wrasse or shrimps.
no easy answers here, and its not all fun and personal preferances either,

 

Some of my fav's

Bllue Spotted Jaw Fish (be careful they are jumpers) Mine did a carpet surfing move and didn't make it
Powder Blue Tang
Yellow Tang
The new Black Ice Clowns (I know you already have a pair though)
School of Anthias (alway give a nice show in the tank)The Purple Queen Anthias are the ones I like
Flame Hawk Fish(reef compatibility says with caution, but I have never had a problem with them)
Then anything that is smaller that will school together is always nice

And thats just my 2cents on this topic

 

The Yellow and Brown should be fine in a 90gal. There are others that will work too,but I would add them all at once as i have read and seems to work just fine.
I am still completing my list also.

 

Yes I seen them online. I like it a lot too.