maybe a white chocolate ganche type icing, you could colour it, did you need to pipe it into peaks? i have a recipie for whipped choc icing, you could just use white choc instead of dark choc. il have a look for it....

250g dark choc
1/2 cup single or pouring cream
70g butter

melt all together in a heatproof bowl over pan of simmering water. stir till melted and smooth. set aside to cool completely. then beat with electric beaters til thick and fluffy.

as i was typing it i was wondering if it might be a bit too sweet using white choc??