One of the requirements for the Hogwarts Sock Kit Swap is to make a bag in your recipients house colours. This can be sewn or knit. It just so happens that my pal is also in Ravenclaw. Do you know how hard it is to find blue & silver or blue & bronze yarn? Even harder to find sock yarn (another requirement of the kit) in these colours. Blue & a silvery grey is as close as it gets.
The plan I had was to knit a blue bag which I would later felt and somehow add the silver or bronze accents with beading (or something).
However a quick visit to the local craft store revealed 10 balls of Panda Starshine in blue & silver! I paired this with some silver metallic thread. Both were used double.
The bag was an idea roughly sketched out with a vague idea of design. It just evolved as I knit.