Hello Kyle Latino,
This is a really good point, and I admit that I have been avoiding it for the sole reason that it means that I have to think through three ages of the clothing of men and elves to figure out what Elrond, Gilraen, and Estel might wear
I agree that having a document of the descriptions of the frame characters would be great, but in the mean time I have found a few fan wiki's that might be of use.
Estel:
http://lotr.wikia.com/wiki/Aragorn_II_Elessar -
http://www.tolkiengateway.net/wiki/Aragorn
Gilraen:
http://lotr.wikia.com/wiki/Gilraen -
http://www.tolkiengateway.net/wiki/Gilraen
Elrond:
http://lotr.wikia.com/wiki/Elrond -
http://www.tolkiengateway.net/wiki/Elrond
I think we might simplify the thought process by imagining that Gilraen and Estel would wear the clothing of Rivendell. The reason for this would be that 1) They are in Rivendell, and that is the clothing that is available to them 2) It would be better to hide Estel by allowing him to be thought an Elf, than to make it apparent that there is a human mother and her child living for an extended period of time in Rivendell. Gilraen could, of course, wear her clothing differently - both because she is human and has different taste, but also because throughout this story she is at odds with Elrond regarding how best to raise Estel - but the garments themselves would be Rivendellian (Rivendellish?)
The next thought process must then be, what is the style of Rivendell? I think to figure this out we need to think about the influences that might exist in Rivendell. The biggest influence is Elrond himself, the next are the people who live there, and the third is the physical environment, and the final influence is its purpose.
Elrond is half-elven, he was raised by Maglor and lived for a long time in Lindon. So I'm thinking there might be a lot of the influence of the sea in the way he would dress. An example of this influence might be that his hems might be ankle length or shorter, his clothing might be smooth and vaguely conical to keep the rain off, another influence might be that he has some jewelry that is sea-inspired. His clothing would also be influenced by Noldorin dress which in this early stage I am imagining as having very fine and complex woven patterns. Being half-elven, he could also give a nod to the Numenorians but I am thinking that might be a small token, maybe a piece of jewelry or a little pouch that he keeps his keys in (or something).
The people who live in Rivendell are many and varied, but I think the predominant influence is Noldorin elves. As I said in the previous paragraph, this might be distinguished by complex woven patterns, or fine embellishments. The clothing might also be precisely fitted, since elves live a long time. I do not, however, think the clothing would be uniform, far from it, I think that the many travelers that come through and the close relationship Rivendell has with Lothlorien and the Dunedan might provide an interesting cosmopolitan feel to the place.
The physical environment seems to be a lush valley in a moderate climate. They would need warm clothes in winter and cool clothes in summer. The flora and fauna of the valley could be represented, and the river and waterfalls could be featured as motifs. The valley is described as having steep walls so the clothing might be functional enough to walk and/or climb around the steep valley.
The purpose of Rivendell is as a resting place for travelers, a place of lore, and a stronghold against evil. I think these functions might be represented individually, depending on the person wearing the clothes. For example, Elrond is a lore master so his clothing might be comfortable for sitting, reading, and singing songs. Elladan and Elrohir might represent the stronghold aspect of Rivendell and their clothing might be sturdy, simple, and functional. There may be elves in Rivendell who like to make travelers comfortable, and they might wear functional clothes with various cultural influences.
These are my thoughts so far. What do you think? Have I missed anything?