Likely sounds that should be added (sorry if there are duplicates or things already covered - I had to scan hundreds of places in ADOM):

• clapping hands in the arena
• arena soundtracks with voices we made up
• something falling to the ground
• knocking sound
• clicking sound
• grinding sound
• rustllng sound
• chuckling sound
• thudding sound
• clattering sound
• sneeze
• icy blizzard
• popping sounds
• giggling
• crunshing sound
• hissing
• clicking
• buzzing
• whispering
• sound of many feet trampling
• water dripping
• grating sound
• Grumph!
• glass hitting stone
• shattering
• Meow!
• people talking in a bar
• cheering
• crushing
• sliding
• chime
• falling coins
• thundering crashes
• mumbling
• ripping
• thudding
• Hurumph! (Dorn Beast)
• slurping
• burping
• bellow
• alarm gong
• horrible wail (banshee)
• *Thumb* (Molochs)
• squeaking
• war cries
• wails and hoots
• high pitched grunts
• grunting roars
• howling sounds
• splashing
• rushing water
• holy chants of a chorus
• wind howling
• casino chime
• casino gong
• casino bell
• roaring waves
• hollow steps
• arcane mumbling
• annoying laughter (clown)
• croaking
• rustling foliage
• crumbling sounds
• clinking sounds
• whizzing sounds
• explosion sound
• distance evil laughter
• splashing sound
• splat
• surprised gurgle
• zapping sound
• squeaking floor board
• toppling stones
• crackling sound
• click like from an activating trap
• wooshing sound
• rumbling sound
• fizzling sound
• knocking sound
• *twip*
• Yippiyaiyay!

Monster voices with no discernible words (if feeling ambitious then in standard, angry, pained and surprised variants; stuff below just copied from the sources):
{"hiss", "hisses"},
{"yelp", "yelps"},
{"growl", "growls"},
{"moan", "moans"},
{"unearthly wail", "wails"},
{"bark", "barks"},
{"scream", "screams"},
{"yell", "yells"},
{"cough", "coughs"},
{"gurgle", "gurgles"},
{"thundering roar", "roars"},
{"high-pitched screech", "screeches"},
{"squeak", "squeaks"},
{"yowl", "yowls"},
{"spit", "spits"},
{"croak", "croaks"},
{"grunt", "grunts"},
{"buzz", "buzzes"},
{"howl", "howls"},
{"hurumph", "hurumphs"},
{"snicker", "snickers"},
{"whinny", "cries out"},
{"babbling", "babbles"},
{"song", "sings"}