For Elizabeth: I may be about to make you a happy person. If you don't mind using tiny pearls instead of seed beads, there's a considerable amount of documentation for designs made from beads on clothing.
Probably the most accessible piece is the "Chichester" or "Butler-Bowden" cope, a 14th c. English work. There's a color photo of it in Staniland's _Medieval Craftsmen: The Embroiderers_, but there's a better black-and-white closeup in Christie's _English Medieval Embroidery_. (I can get exact page cites if you need them, but my notes are at home, and I'm not.)
The basic technique is to lay down the shape you want with white silk thread, and then cover the entire design with seed pearls. Some other English pieces of the same era show evidence of having been worked in this way, in that the white embroidery is still there, as are the threads left when the pearls were snipped off.
I have one piece of visual evidence for the use of this kind of embroidery on secular clothing from the 14th c., and a few that are later. The painting _St. Ursula and her Virgins_ (don't recall the artist; I'll find it for you if you want) shows one of the virgins wearing a purple cotehardie, the torso of which is covered with phoenixes. Having examined a plate of the painting closely, I believe that the phoenixes are worked in pearls and red (silk?) embroidery. One piece of 16th c. evidence is a portrait of a German count, who is wearing a doublet embroidered with pearl crescent moons.
There's also some evidence from inventories. Mary Stella Newton (in her _Fashion in the Age of the Black Prince_) quotes a number of Great Wardrobe inventories that list pearl-embroidered items, usually hats or hoods but sometimes mantles as well. For example the Dauphin of France had a hat worked with pearl leopards holding lozenges with his arms.
I apologize for the half-citations of my sources; unfortunately, I'm working from memory here. Drop me a line if you'd like proper documentation.
Hope this helps...
*Ex Ungue Leonem*
Medieval Beadwork Page by Lady Elspeth Grizel of Dunfort - There's no point in my doing anything more with this page, because Grizel's page is so incredibly comprehensive! Includes patterns and how-to articles with photos!
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SCA-ARTS ListServ Citation Index on Beading - Go here for LOTS of tasty links
Rialto Thread on Beadwork
Center for the Study of Beadwork
The Bead University