I totally agree with Procession.
I don't know anout you guys, but when i saw the design for the G5 (both inside and outside), i was in love.
Anyway, i think the ideas that were posed in the infamous Nexus mock-up were good. The N5 needs to be smaller than that of course.
4 controller port receivers (wireless as standard), 4 GBA2 wireless receivers, and 4 USB ports for the memory card (those USB memory sticks are getting to be quite popular, so Nintendo should make one of their own, with greather capapcity), and perhaps keyboard and mouse.
The medium should be DVD, with the same (but more advanced) anti-piracy encyrption as the GC mini-DVDs.
Under the console should be the ports for any future add ons, like modems (which should be ready at launch, if not within the first year).
The DVD drive shouldn't be a slide-out sorta deal like on PCs, the PS2 and XBox. Have some cool lid design where you push the button and the lid slides to the side or something (have a look at those modern CD players in shops).
All in all, make the console as wireless, sleek and modern as possible. IT doesn't have to fit in with other entertainment devices. The console should be a design of it's own. It should stand out i.e. turn heads.