I stole this idea (of building a costume in multiple layers) completely from Amy Ganter, she's got a great webcomic called Reman Mythology which you can find here:

Reman Mythology

Really well-designed, excellent comic, worth checking out.

There are a few vulnerabilities I left open in the design, notably the knees and the underside of the arm, as well as the torso immediately under the arm (this is a problem even in modern, real-world body armor like Kevlar vests and the like). His upper arms should probably be encased much like his thighs, but oh, well...

The armor attaches with a series of buckles and ties... the buckles allow for a small size variation in the person wearing it.

He might wear a backpack, but he keeps a lot of items in the various voluminous pouches that are all around his belt, such as things to care for his weapons (whetstone, oils, cloth, etc.), small items that may contain magical healing powers, keys or money or whatever other little bits the character might need. The horn can be used to communicate with others over a distance by the use of various signal blasts. Since this fellow is using a large, two-handed broadsword, he uses no shield, but a small buckler might work well.

-EDIT-

A transcription of the notes is as follows (with the exception of the parenthesed comments):

1)
-hair cropped for sanitary purposes.
-tunic and pants are made of a thin but durable silk-like material (silk was famously used by Asian warriors for it's durability and breathability).
-pants are laced from top to bottom to allow access for nature's call (reason being that it's easier to reach the bottom of the laces beneath armor than it is to reach the top when in full kit... after getting dressed up it's not the time to find you want to take a whiz).
-socks are about calf-high and made of a heavier cloth at the toes, heel and sole.

2)
-heavy padded jacket, tied at the sides (quilted jackets were usually made of wool and helped to cushion the armor. I'm sure they smelled godawful).
-heavy boots with armor plating at the toes and top of the foot permanently attached.

3)
-almost full extent of elbow motion (I don't remember if that was to mean that this WAS nearly the full extent, or it ALLOWS nearly the full extent)
-leg armor attaches to garter belt over padding and by buckles at sides
-sleeve poking out (helps prevent chafing at the wrist)

4)
-light scale and banded mail protects sides, belly and groin with minimal loss of motion (this is loosely based on an actual Roman design)
-sometimes the fingers and the back of the hand may have plates sewn onto the fabric
-vulnerable spot (referring to the point where the thigh armor narrows above the knee, a design flaw on my part)
-heavy gloves
-side plate to help protect hamstrings (seen frequently in gothic plate)

5)
-buckles to adjust fit, NOT attach armor
-breastplate actually hinges at shoulder
-ties under arms, buckles over shoulders
-ties again

6)
-leather coif and gorget to help protect neck and head (for better protection chain would be used, but it's a lot heavier)
-horn is useful for signalling others in the heat of battle
-pouches may hold various items that come in useful, such as healing items or enhancements
-loops for holding sword scabbard (also, I believe, referred to as a "frog", don't ask me why... anyhow, this allows you to remove a sheathed sword without undoing the whole belt)
-for some, this is a full surcoat (as opposed to the sort of kilt thing he's wearing, which may still bear a coat of arms or other identifying symbol)

7)
-two-handed broadsword, 40" blade, approx. 10 lbs (which, as I later learned, is way too heavy)
-armsman's helm, offers some protection from rain and provides excellent visibility (also based on a real item of armor, though the brim was rarely so wide I think)


So there you go... lots of semi-innacurate imagined details.