A naso will get waaaayy toooooo bigggg (over a foot) for a 90g reef tank. They eat lots & poop (technical term
) lots. Should stick with selecting a smaller tang.
You can also keep several small blennies & gobies together since they are generally peaceful. Just make sure they occupy diff. ecological niches (ie. mandarins need pods & mysis usually, while lawnmower blenny's more of an algae eater). Lots of LR & places to hide. Yellow watchman & pistol shrimp pairing would be cool (cheaper to buy separate & pair in your tank than to get already "paired" specimens).
Angels - the Genicanthus family are considered reef-safe (planktivores)
Dwarf angels - some are, some aren't. No guarantees that the lemon peel or coral beauty won't start nipping at your polyps.
Dwarf dwarf angels - Cherubs are beautiful although pricey for a fish that looks like a damsel, but full of personality. Mine was reef-safe.
Heniochus (bannerfish) are one of the few butterflies with decent survival rates in captivity & are reef-safe.
In a 90g, I'd stick to one or two med-large "center-piece" fish, and several smaller ones for added life, colour and activity. Remember, the more fish you add, the harder you'll have to work (or better filtration you'll need) to make your corals thrive.
JMO
Anthony