I was talking to my friend about this the other day and we think the old Police Box thing is way outdated. Dr Who should have something more in keeping with the times, but seeing as most phone boxes are transparent these days we humbly suggest the BBC consider using something like a Portaloo as the new TARDIS (seeing as my pal is a builder, they're affectionately known as a "Turd-Tardis" on site).
In keeping with the Tardis of old, the decor should resemble that of a very plush (and spacious) boardroom lavatory inside, complete with gold taps and expensive tiles all round.
I heard a rumour that the first episode of the new series involves the Doctor making an unfortunate visit to Glastonbury in his new Tardis...