This page has photos of actual 19th century garments, which I find useful for inspiration.
Most of these photos were found on eBay and antique garment dealers, like: Maire McLeod Elegant Vintage • Karen Augusta Antique Lace & Fashion • Antique & Vintage Dress Gallery • FiddyBee • Time Travelers • 1860-1890 • Rupert & Toby's Collectables • Carolyn Forbes Textiles & Vintage Fashions • Old Threads Antique Textiles.
Another site with lots of excellent images is Démodé: Extant women's clothing 1750-1919.
Click on thumbnails to view larger images.
Beautiful pink silk organdy dress, c.1870
Lavender silk gown, c.1870
images courtesy of Maire McLeod Elegant Vintage
Calico bustle gown, c.1870
Young lady’s green silk taffeta dress, c.1870
Blue silk taffeta bodice, c.1870
Black jacquard basque, c.1870
Pink organdy dress, c.1870
Teal silk gown, c.1870
Wedding gown w/ lily trim, c.1875
Red & black gown, c.1875
Silk taffeta gown, c.1876
Gold silk taffeta dinner gown, c.1876. Gorgeous!!
Silk taffeta gown, c.1877
Moire silk wedding gown, 1879. (The photo is of the woman who owned it.)