The Florida Educational Technology Clearinghouse has an extensive collection of out-of-copyright clipart, much of it from the 19th Century. Of interest to us is the Civil War section (there is also one on Reconstruction), which has a lot of period illustrations from sources like Frank Leslie’s. All are available in various resolutions to fit just about any need, and of course they are free. Here’s one of the death of General John Sedgwick at Spotsylvania, which is more accurate than most.
Worth a look for your next project. For best results go to the search page and enter Civil War as a keyword.