Nice, I'm going to have to try this out! A couple suggestions: the Kindle2 can do 4-bit greyscale, so you might want to make a new greyscale map file to support that. Also, I find it nice to pack the images into a .mobi file so you don't have to rely on the image viewer interface, which seems rather buggy to me (also you have the opportunity to create a table of contents). Mobiperl can do this, but it is a mess. The official mobigen program works great, and it is command line so I'm sure it would run just fine in wine.
If you haven't seen it already, check out my conversion post (unfortunately it is somewhat windows-centric). I agree, rotating is the way to go.
https://www.mobileread.com/forums/showthread.php?t=40882