The T-206 series of tobacco cards from the 1910ish time period is iconic. It includes the famed Honus Wagner card, as well as a Ty Cobb variation (with the Cobb back) that is thought to be even rarer. Now your historical OOTP leagues can have these, too.
Download here:
1909-1911 T-206
The file is large as there are 36 unique card backs, randomly chosen such that the relative likelihood of any particular card back appearing is somewhat comparable to the real life distribution. I've actually found it kind of fun to see which card back players end up with.
All files have been prefaced with a "t206" name, so they can be put in your bb_card template folder and play nicely with everything else in there.