You have a potentially rich world of non-visual sensations with which to play, and unique situations to explore! I actually envy you the potentially-rich experience of writing this!
You have other senses--- sound or hearing; smell; feel or textural variations (presuming your character[s] can or will touch each other, or those with whom they'll interact); along with those very astute suggestions already provided!
I've an Israeli friend who was blinded in a terrorist bombing in the mid-1970s. He had participated in the martial art called Krav Maga. After becoming able to get about, again, he worked with his instructor and several students to perfect a "Blackout Krav Maga:"
It's amazing how one can zero in on others without needing sight--- people make noise all the time, whether simply the sound of the rush of air as they breathe (stronger if winded or frightened!) plus coughs, wheezes, whistling from breathing through a deviated septum; along with the very common "creaking" of knees and "cracking" of joints not to mention the sounds of footsteps (many people drag their feet; slap down their toes when stepping; "kick" the floor with their heels; plus shoes [even 100% synthetics!] will creak, squeak, crack, pop, "Click" because of hard-plastic or metal heel-pieces, and more)
Actually, some people even carry on a continual whispered monologue! No, they're not barmy; this is their way of "thinking." Only instead of it being a nonverbal process, they'd begun to "articulate their thoughts!" (This is rare, but could be made into a unique character identified as "Whispering Gael" or the like!)
In addition, what people wear as well as carry are also abundant sources of sounds. Cordoroy, silk, and other fabrics make noise when surfaces rub together; leather and webbing accessories will almost always creak as one moves---sword baldrics or equipment belts; burden straps; shoulder-slings, and the like. Also, the impacts of twigs (or, underground, roots) will make metallic noises when striking against helmets, plate-armour, shields, and such-like as the wearer moves along.
Plus, "personal items" can always make noise: Coins jingle in pouch or pocket; things analogous to ID tags can make noise--- necklace medallions, metallic charms, and other devices. Keys are also classic noisemakers--- the Seneshal or Bursar; a head servant like the more-contemporary butler, will carry keys as a "badge of office," and this can be seen by your character(s) as somebody like "'Mister Clink-clank,' the one who can get to the best wine and cheese!" (They may even silently shadow him, hoping to filch bites or sups of cheese or wine from the hoard!)
Then, there are the thousands and thousands of different smells! This is something I've personally noticed: Different ethnic groups prefer to use different spices, and differently prepare often vastly-different types of foods, which in turn almost always makes "native" body-odours very different.
In Victorian times, people simply assumed "different Races smelled differently;" well, people actually did--- but it was NOT because of genetics! It was simply "cultural," in the end.
People who eat large amounts of red meat will have very different "aromas" from fish-eaters, and this differs from those who, by reason of economics or perhaps religious proscription, eat mainly/only vegetables and grains.
Then, consider different occupations: In a "Middle Ages" setting, soldiers would be enveloped in the combined odours of old spilt blood and body-fluids, stale sweat, musty & moldy leather, and the inevitable "rancid old oil smell" from cheap oil used for leather-dressing and weapons-rustproofing.
There are also many other examples: Men who care for horses would smell like strong sweat, and the stables; blacksmiths will have a strong odour of coal- or charcoal-smoke, a strong aroma of sweat; and the "hot metal smell" that's peculiar to smiths. Butchers would wear the aromas of an abattoir or slaughterhouse, being the strong smells of old blood, offal, and incipient decay. Cooks, of course, would be enveloped in food- and spice-smells. Turgeons or doctors (going from historical human prototypes) would stink of old pus and blood, herbal concoctions, smokes of herbs and grasses, [and despair.]
Barkeeps would smell strongly of food, drink, smoke, and sweat. Barmaids (possibly prostitutes too) would smell of many liquors and beers, as well as many men; plus, probably, inexpensive perfume-herbs such as lavender and sweet-grass. Noble folk would be the ones heavily anointed with "expensive" floral scents such as rose-water or orange-blossom-water, as well as extracts of lavender, and other sweet-smelling herbs to cover their smells of sweat. Probably, the "lordly types" would have stronger sweat-smells because of frequent sword-practice, and an undertone of sword-belt and blade-oil aroma. In the Middle Ages, many if not most "Nobs" and knights took part in daily sword-practice.
The nobility may practice the Greco-Roman habit of "oiling" the body with olive-oil, followed by using a bronze or horn "stigil" to scrape off dirt, sweat, and excess oil--- this would put an olive-oil odour on these worthies.
Open your mind to think deeply, and you will realize that every profession or way of life found in the Middle Ages will have almost-unique "professional aromas!"
Combining some of the examples of "non-visual identification" in a sort of third-person narrative (as in WATERSHIP DOWN) allows you to create mental images of characters in the readers' minds every bit as memorable and impressive as any visual description!