@DDRBoxman: eips -f -g handles PNG8 just fine

.
You do have to make sure they're reaaaal PNG8, and not indexed, but apart from that, it works. Can't remember if there's a way to make it behave with JPGs.
See
this post and its two links for the one-liner I use with ImageMagick to process stuff that will work through both eips and the framework's usage of libpng.
EDIT: As for reining in the menu, look at
KOReader's startup script for all the various ways to achieve that depending on the device & FW combo.
A TL;DR version that may not be too invasive: sigstop whatever's handling the screen updates (i.e;, cvm on legacy devices, awesome otherwise).