found it, it's affiliate=mondadori (the store name).
changed it to kobo, and now the screen is blank, with a little "sleeping" tag on the lowerleft of the screen (is this the default screensaver for kobo purchased readers?)
-with affiliate=kobo (screesaver)

(Click to enlarge.)
-with affiliate=mondadori (screensaver)

(Click to enlarge.)
(when shut down, it's identical to the screensaver, but inverted colors)
also, during bootup, there's another image with a "kobo in" in place of the symbol, comming out to be "kobo in mondadori".
so there should be at least 2 if not 3 different images hidden somewhere. (i would have agreed to the fact that it could just be a normal font written on a blank screen, but that symbol implies graphics)
any further ideeas of where/how to dig?