and another
If you made a rectangular sponge, sliced off the top part for a "lid", covered both bits in rolled out icing and then decorated with either icing pens or the powder/liquid colours that would make the box. It looks like they've used satiny fabric for the lining on this one. You could then mould a shoe from the rolled out icing or, like I said, cheat and buy one .
If you make a shoe you could decorate with anything really as that bit wouldn't be for eating anyway (sequins, crystals, feathers!!)