I looked at fashion plates and consulted Costume In Detail and Nineteenth Century Fashion In Detail and finally decided to make a drawstring, lightly gathered neckline and smooth elbow length sleeves. I didn't want to make a plain white gown, though they are far and away the most common kind to find examples of. I ended up finding a fabric at Wal-Mart with a white ground and blue figures that was $2/yard. I did find quite a few original printed dresses and genre paintings of printed dresses, among them were these:
Portrait of Jane Ann Campbell 1820
Girl's Dress 1815
14 year old Mary Ann Gale painted in 1815
Cotton dress 1805-1810
I took Rebekah's regular dress pattern and made it up in scrap fabric and then drew the new, further back shoulder seams in magic marker. Then I drew and redrew the slanting back seams to get the placement and angle right. I'm used to the curving back seams that were popular in the 1860s, whereas Regency seams are more of a straight line. Then I tweaked the armscye, cutting it in deeply at the back to give the illusion of a "small back" that was popular in this era. I cut the bodice apart on the marker lines and redrew the pattern with it, adding seam allowances.
When making up the dress I lined the bodice in a light weight cotton and piped the back seams. There is a casing at the neckline with a tiny 1/8" twill tape drawstring and self fabric buttons closing the rest of the back.
The sleeves were the hardest thing to draft of anything I've ever tried. I drafted and tried half a dozen incarnations of this sleeve before getting even remotely close. I looked at my Patterns Of Fashion book, but it wasn't very helpful. In the end I traced the whole sleeve opening shape by laying the dress flat and tracing it onto paper. I then stared at that for about five minutes thinking, "well that was brilliant, what do I do now?" And then a little line here, a little curve there and I came up with something passable, though not perfect. They are elbow length sleeves with the small amount of excess held in with 2 pleats and a self fabric button as trim.The skirt is smooth across the front and full at the back, slightly gored and just above ankle length. The back skirt opening is made from a solid length of fabric, sliced open about 5" and turned under in a tiny hem. This was nice because then I didn't have to sweat matching the print like I would have if the skirt back was 2 pieces seamed up.
She really seems to like it. :) She has a bonnet to go with it which is as of yet untrimmed, hence no pictures, but I'm working on it.