Yeah, I love those old time chapter headings too. And, okay, I didn't weep, but I was pretty discouraged for a few minutes. So, I've heard about DPI, I know about compression, about resolution, but I never had to take something I'd messed with on the web and try to blow it up.
On archive.org I would download the largest jpg they would let me work with. But when I wanted to blow my map to 18x24, it was a no go. The guy at the shop told me he needed closer to 300 DPI and my pic was 70 something.
Luckily it worked out okay for my session because the 11x11 that I had printed up looked like a legit scroll. But, now I'm thinking of doing all map work in svg. I have Inkscape and will try to learn it. It looks like I can embed a bitmap in a svg file and it will scale it with some aliasing. Any of you digital wizards want to weigh in with your experience/suggestions?