Very strange. I definitely don't have any inverted images, and I can recognise the images that are being inverted when the Kobo automatically goes into PowerOff and they are the same ones that show up correctly when I manually PowerOff.
The only mods I've put on are the Google Analytics avoidance one, and I have also added the Metazoa firmware patches but with only three patches enabled (line spacing values, custom left & right margins, and increased Book Cover size in library view).
I'm very happy with it anyway, as I can avoid it occuring my manually powering off. Just makes me a bit curious as to what might be causing it.....