As far as I know,you can add 3rd party application icons in Carbide UI,as long as you know the program UID-s....
Here's how..
To skin icons in the Carbide.ui, that are not defined there by default, choose from the menu:
Window->Preferences
On the left side choose: Carbide.ui->Third Party Icons
Specify the Application UID and Name. The UID identifies the icon in the phone, the Name will be only displayed in the Carbide.ui (it does not change the name on the phone).
Here are some of the UIDs of Nokia applications and applications that are very often preinstalled in the device that are not predefined in the Carbide.ui, in alphabetical order:
Adobe Reader 20001bb9
Flash Player 101fd693
Snakes 10208a45
Sports Tracker e4935e8
Team Suite 101f8f3c
Tutorial 10208a86
Wellness Diary e4935ea
WLAN wizard 10281ceb
This is the window....

Hope I've helped...