The only problem with making the iBook look like the iPod is that it already does. They both have the classy white-plastic look (and, in fact, I think the iBook had it first). The only thing the iBook doesn't have is the mirrored metal back ;-) and that might be a little strange.
It might be interesting to see an iPod mini-looking subnotebook/tablet, as some have mentioned in other threads, but I don't know what else from the iPod line can be ported over to the iBook's style.
I admit though that the iBook has probably gone the longest without any serious changes to its look. Mine is from January 2002 and it looks almost identical to the new ones. They changed the way they do the white so it doesn't look as translucent on the new ones, the font for where it says "iBook" under the screen has changed, and the new ones have a slot-loading optical drive. That's about all they've changed aesthetically in a LOOOOONG time.