Hi there. I've recently been inspired by a cake i saw online, it had a shimmery design piped onto the side of the cake, kind of like a paisley design all the way around the sides. i wanted to know if anybody knows what to use for the piping. Should i use buttercream? and if so, how do i get the shimmery effect or metallic effect to give it a bit of bling? Would appreciate some help from anyone who knows! thanx xx

I would use buttercream and a very small tip.  If you have a buttercream cake and use royal icing, the icing will darken from the buttercream.

If I covered a cake in fondant, though, I would use royal icing.  For the shimmer, I would use a very,very small paintbrush tip with luster dust.  Or even a q-tip.

Sounds like it will be beautiful.