I think you can as long as you've masked the cake with either a thin layer of fondant/marzipan or buttercream to prevent the cake from drying out. Freeze with out the ganache though, its not very pleasent trying to cut through a hard layer of ganache when its on a cake.
The problem would be the creases you will get in your ganache. Also when melted ice gets on it it will leave spots. You can freeze before wrapping in plastic, Unwrap before you thaw & use a butane torch on the whole cake to smooth out & get it glossy again. I have done this many times.