Kings of War is a new set of fantasy rules from Mantic Games, who make some very cool figures. But the rules are non-figure-line specific. And they’re free.
rules
De Bellis Indica DBA Variant For 18th and 19th Century India
De Bellis Indica is a DBA variant for warfare in India in the 18th and 19th Centuries.
American War of Independence DBA Variant
From Paul Potter, a variant of DBA for the American War of Independence.
Horse and Musket DBA Variant
Here’s a Horse and Musket DBA Variant — primarily for Napoleonic and Seven Years War, but since the basic principles of war in that era covered a huge number of conflicts, you could adjust as needed.