Note2 and ebook practices to get best illustration

I've got a Note2, and have found that illustrations in ebooks (b/w drawings, but also some gray scale and color illustrations, as identified with Calibre's ebook viewer) tend to be at small scales, or not as crisply rendered (i.e., resolution) as I thought I would get with a high resolution screen. Some of these illustrations have include:
- japanese woodblock prints, reproduced in current ebooks published in 2013
- Gustave Dore illustrations in Dante (Inferno, Purgatorio, Paradiso) obtained from Gutenberg.org
- Maps and drawings in current ebook publications of LOTR.


I use epub as a standard format for all my ebooks; is there some setting or optimization I should make in the Calibre conversion to create a better file?

Or, is there some setting on the Note2 to better render illustrations?

I also use Moon+ as my primary ebook reader - are there some setting there to optimize illustrations

I realize these are very broad questions, but I'm not sure (yet) what the problem is, or if there is a problem. Any suggestions about best formats and practices, or references/links to threads in other forums, are appreciated

TIA
Ed