Can you freeze icings? What types freeze well and don't (i.e. royal, buttercream, gumpaste, fondant)?

Also - can you frost a cake and freeze it?

Let's say I wanted to crumb coat cakes or frost and freeze - then thaw them when ready to fully decorate - can you do this?

sure to the third question. However, I just freeze the cake and then pull it out and fill and frost,

Hi there,

If you use Indydebi's BC, no need to freeze. But i have frozen that and other BC. Do not freeze RI and gumpaste. Nor does MMF freeze well on it's own.
However, I freeze cakes all the time that are covered in BC, or BC and fondant. You just have to ensure they are wrapped well . I use Glad seal and wrap- it's great! I have even used WASC, covered in BC and frozen without seal (just in my cake container) and it was fine...
When you cover a cake in fondant and freeze it, let it come to room temp (at least an hour) with the wrapping on, then remove the wrapping so the condensation will adhere to the wrapping. Then let it air dry until it's no longer tacky to the touch.
I also freeze cakes then fill then. You have to let it settle a bit (an hour at least) however, then crumb coat and cover in fondant. HTH!

I freeze buttercream all the time