Since I love newspaper strips I'll mention this.... The Library of Congress has tons of public domain scanned newspapers online here:
http://chroniclingamerica.loc.gov/newspapers/. I've spent many a night picking a random paper in a random city in a random month and year to see what strips it had. I've added many from that site to my digital collection and share them all on DC++. Strips back then weren't published like they are now. The vast majority only lasted a few months to only a few years. It wasn't like today where a strip like "Katzenjammer Kids" is still active since the late 1800s!!!
Anyway, the papers can be viewed at fullscreen so the strips can be copied via PS or GIMP and made into whatever image format you want and saved for distribution. Everything there is PD with the obvious exception of things that have had their copyright renewed.