The year is supposedly 1289, but the outlook and structure of the world are somewhat closer to the Renaissance, with an incorporated city and the Guilds and whatnot, so we can't just take our costuming ideas from 13th century Britain. There are also a lot of 'barbarians' around - the Norscans still occasionally raid these shores, and the different races aren't going to drop their style of dress just because human fashions have changed.
Women's clothing in Treasure Trap seems to tend towards the Renaissance end of medieval, though this may partially be my fault for favouring bodices over chemises and shifts.
Women's clothing in Norman times consisted of reasonably tight-fitting robes or dresses belted in at the waist, often over an undertunic or with a cloak over the top, or both.
Fitted bodices started to kick in around 1400 and continued to get tighter and more corseted into the Elizabethan period. Note that pictures you'll see of stereotypical women's clothing from the 15th and 16th centuries will be of very rich ladies, and that most dresses were far less ornate.
It should also be noted that women can get away with any more typically male costumes if they want- collarless shirts, trousers and tunics are all fine.
In all these cases, richness of clothing is, I find, often better shown using braid, trimmings and jewellery as the range of fabrics available to us is so much wider than that available in 1400!
Men's clothing in Treasure Trap can range from Saxon to Renaissance without much trouble. Here are a few ideas of things that go together - Requiem certainly had no idea about costume when he turned up at TT, so this may be helpful to others.
Costume for a new attendee is fairly simple - black or brown or blue, no logos (a T-shirt inside out will work), black or brown trousers (no blue jeans please) and shoes that aren't white trainers.
What seems to be the standard outfit for men in Treasure Trap consists of a shirt without collar or cuffs, and a pair of leather or other stout trousers (not blue jeans, though black or brown jeans are acceptable). A belt around the waist, outside the shirt, helps to give the outfit some shape. Leather trousers are chosen because they afford a little armour protection as well as looking a bit less anachronistic than jeans. Full-length robes are often preferred by mages and other less martial types - they need little else other than a simple belt. There is a fashion for cloaks, because they are effective and easy to make.
Saxon nobles tended to wear a knee-length tunic that was split up the sides to allow mobility, combined with fairly baggy trousers, which may then be cross-gartered (bound tightly to the lower legs). The whole may be combined with a simple cloak, made of a semicircle of material gathered at one shoulder by a heavy clasp or brooch.
Norman men wore fairly similar apparel, but their tunics were not split up the sides (that I can tell) and they disdained trousers as barbarian clothing. They either went bare-legged or wore long hose (tights / leggings), possibly particoloured. The richer the man, the longer and less practical the tunic, and the better fabric it was made from. Sleeves are not tapered.
As one progresses to the High Middle Ages, the tunics become longer - they now reach the calf or ankle, and are split up the front for mobility; sleeves are fairly strongly tapered. This would be worn with hose or leather trousers, and belted at the waist.
An undertunic is worn with all three of the above styles, but this would probably be somewhat over the top for our interactives (which can get quite warm) - we are not re-enactors, and are more interested in looking approximately IC than in actually reproducing it all accurately. Similarly, we don't really care what fabric things are made of as long as it looks nice.
Renaissance clothing is different again, and I don't know much about it - see Maelstrom for ideas here. Basically one wears a doublet or other pretty coat over one's shirt, then short trousers, still with hose underneath.
The people of TT tend to go bare-headed, unlike those of the Middle Ages - there are a few hats and coifs and such in evidence, but most people tend not to have head coverings beyond the hood on their cloak.
Kender are the only race where the racial physrep is mostly described in terms of clothing - the only unifying thing about their clothing is that it is brightly coloured! Although, to be honest, the colour of kender clothing could hardly be said to be 'unifying' as their sense of taste seems to differ from that of all the other races.
Elemental elves (and, indeed, mages) tend to wear the colours of their element; they also tend to wear rich fabrics as the elves tend to consider themselves to be the ultimate in nobility. Dwarves tend to be attracted to heavy armour and practical clothing (I'd probably go for the Saxon end of things if I were trying to be more adventurous).
If you're from Norsca or Gaul, there are many resources on the internet about Viking or Celtic clothing, aimed at reenactors. Our standards are less exacting than theirs, but that doesn't mean we don't appreciate good kit.