For ONE WEEK ONLY the Commercial Pattern Archive at the University of Rhode Island is offering free online access! Login with the username "guest" and the password "pattern".
COPA has about 48,000 vintage patterns (including the small scale pattern piece images!) dating from 1868—2000. Believe me when I say you can be there ALL DAY. (Instructions for searching their archive are here.)
The cost for a full subscription, for individuals, is $120/year — a bit pricey. But think of what you can find out in a week!