Indeed... QUite a few examples remain, such as the Mexican War/"Kibbler" packs that seem to have been the most common, the so-called "hard packs", the imported Trotter pattern or "Isaac & Campbell" knapsack, and the M1855 Federal packs scavenged from battlefields and Federal supply points. Quite a few references are made to them in the ORs and period accounts.
So yeah, I have an opinion... or were you looking for something more specific ?
;-)
Tom