Just use modern logical markup and let the reader decide. As many have mentioned, background images don't work well for ereaders. If you're attempting to read in sunlight, background images don't work well for tablets either (since it diminishes what little contrast you do have). On top of that, there are ereading apps for tablets that let you change the font and background image, to give you a vintage or modern appearance.

For what it's worth, I agree with tubemonkey: a font is a font. They only time the font annoys me is when it's hard to read.