I've searched in vain for at method for changing a footer logo dependent on page number. I want a different image on every other even page but as I am already using a number of master pages to different chapters for the book, I want to be able to vary the footer without having to apply different master pages.
Could using XML in combination with text variables do the trick?
This would take a custom script, no question, because it requires conditional logic, which you don't have available with XML.
Your best bet would be to ask on the Adobe InDesign Scripting forum, where lots of very helpful folks hang out. (Scripters in general are some of the most helpful people you'll come across on the interwebs.)
It might be a bit funky, but you can make a 4-page Master. Thus your Master includes two spreads, one for each of your logos.
The trouble is that the Indesign wants to keep facing pages, so I had to manually drag them in place. Otherwise you only see the first two pages.
Once you have the 4 you can duplicate them to fill your page count.
The other problem is that you might have to allow more page size for bleed, as there would be no bleed between the two spreads in this set-up. (on the middle edge between spreads)
Shift+Ctrl/Option+click it on the actual pages, and then place the image?