Quindia Studios has a basic American Civil War painting guide.
For American Civil War games, here are some print and play casualty counters.
Legion Wargames has a Fire and Fury Scenario for Chickamauga.
The Photographic History of the Civil War is a classic work available now as an ebook, in pdf format and in other ways online.
Thanks to reader FNH for the tip!!
Here are a page of downloadable, printable flags for your American Civil War games. They’re quite nicely done.