These days, photographing a dress on a mannequin (à la Costume Close-Up) would seem to be the best option to accompany a pattern. Unfortunately, I don't know where there are any mannequins that will fit Victorian clothing - you may remember the issues with Great, Strange, and Rarely Seen? So drawing is the only option. But I haven't taken an art class since eighth grade! Practice is necessary.
I started out just trying to draw garments I'd taken pictures of as though they were on a body. This was ... not encouraging. Anatomy is difficult, and there's such a jump between a garment lying flat on the table and on a body that you basically need to be able to draw straight from your imagination to manage it (which I can't). So I went looking for croquis.
|:/ and the one in the upper left is a copy of a Waugh sketch|
|Left: the mourning gown; Center: another I plan to pattern|
|More from the Chapman|
|Left: Les Arts Decoratifs 49-32-48.ABC; Right: MMA 2009.300.3009a-d|
|MMA 1985.138.2a, b|
|MMA CI.63.23.3a, b|