Thanks to Mike Hayton we now have the Guide specs availalable for MC. As part of those specs there is support for Channel Logos and one kind soul at TGB has released a little app to add them into the guide. http://thegreenbutton.com/forums/permalink/333270/333270/ShowThread.aspx#333270
The latest version of MyChannelLogos is available at www.mychannellogos.com
If you want the Channel Logos I've created you can download them here
Download Freeview NZ White Logos Updated 14/10/12
I think it looks pretty nice.