You can customize the icons and colors of your toolbar with the following Quero Themes:
To install a Quero Theme download and save the theme file to your Quero directory, click on Quero > Options > Appearance and specify the location of the file. You must restart IE for the new theme to take effect.
Quero Themes SDK
To build your own Themes download the Quero Themes SDK and follow the instructions outlined in the readme.txt file.