Thanks, Dale -- and everyone else -- for your help! My apologies for being slow in replying, but some stuff came up recently in my life that needs to be addressed, so for the moment I don't have much time to spend on this. Hopefully I'll be able to get back into it more in a few weeks.
In the meantime, thanks also for pointing me to that "Ebook Covers" page -- I'd seen that, but I guess I didn't realize that what it describes is also applicable to any full-page images one might want to display in middle/body of one's work, too.
Interestingly, however, I've already been using essentially the same code that's shown on your wiki page about that, except that what I've been using also has some additional styles and stuff that takes into account that "some e-readers insist on adding margins and other padding to each page" (to quote from the following site where I got the code I'm using from)...
http://denis.papathanasiou.org/2011/...image-element/
Like I said, and as you can see, this seems to be pretty much the same, but "better".
HOWEVER, that's also exactly the code that works great in iBooks (on the ipad), but "breaks" in Kobo, with those large images getting cut in pieces over separate pages.
I haven't tried any other readers -- although I noticed in your sig, Dale, that you're "currently using an EZ Reader or a Literati". Maybe I should check those out, too, if only to see how else my experimental first epub is totally falling apart.
Once again, thanks so much for all your help! I do have some other things to address in my life at this time, but even if I "disappear" for a while I will be back once things settle down again... I hope.