Here is my shortcut bar-

The book icons are pretty self-explanatory. Some of the program functions are cryptic, but I've memorized what they mean. (But a more graphically intuitive set of icons for program functions would be REALLY nice.)
The last two icons are for links to web sites. These were created by dragging the Firefox blip from the URL line to the L4 shortcut bar. They are ridiculously incoherent.
Simple question: Is there a way to customize these icons with something more meaningful? Is there a way to add custom icons to the list available in L4?