While there are no favorite channel icons in the remote currently (hopefully they add some as there is a Favorite Channel icon option in the image browser), you can easily add custom buttons. You may have to search for the channel icons you want or make some yourself. You will have to resize them. I believe they had to be one size on the MX880, but am not 100% sure. The MX890 definitely does not have to be one size. I tried 88x59, 114x76, and 135x90. All three sizes worked, and displayed fine on the remote. If you go too large though, the buttons will not have proper distance between them. 135x90 would be considered too large for me as it extends beyond the midpoint of the screen. You will then have to place the icons in a new folder that you will place under:
C:\Program Files\Universal Remote Control, Inc\Complete Control Program\MX-890\Images\Buttons & Backgrounds\Custom Buttons
note: This is the location of the folders on my WinXP machine. It may differ on yours. The Custom Buttons folder is a new folder I created. From within CCP, you can create a button
It's very easy to do and the bulk of your work will be finding the right icons and resizing them or creating new icons on your own.