do you have any folders on your bookmark toolbar? is it boring? are you a complete customization freak like i? THEN LOOK NO MORE, after hours of sorting out how to do it from many sources i have it all in one location!
does that look good to you?
well here is the code:
[code]
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
.bookmark-item[container="true"][label="
"] {
list-style-image: url('file:///') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
}
[/code]
simply download Chrome Edit (http://webdesigns.ms11.net/chromeditp.html) plus add on and get down to work, go tools >Chrome Edit Plus > chrome edit, and on the first tab put in that code...
you only need to repeat the first line "@namespace" once, the .bookmark can be repeated for every bookmark toolbar folder you have.
First find an icon you want (i resized some dock icons i downloaded) and resize it to 16x16 with a PNG file and transparency (if you want). Next place the icon in a folder to keep. Then replace the with the name of the folder on the Toolbar EXACTLY. Then replace the to the location on your HDD that the icon is (ex. F:/Other/icons/firefox/hardware.png).
Once you have done that for all the icons you want, click save on the bottom and then click restart! and next time you boot up firefox check your bookmark toolbar 
Post results 
heres my code for reference:
[code]
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
.bookmark-item[container="true"][label="Computer Hardware/Tech"] {
list-style-image: url('file:///F:/Other/icons/firefox/hardware.png') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
}
.bookmark-item[container="true"][label="Gaming"] {
list-style-image: url('file:///F:/Other/icons/firefox/gaming.png') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
}
.bookmark-item[container="true"][label="Photoshop"] {
list-style-image: url('file:///F:/Other/icons/firefox/photoshop.png') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
}
.bookmark-item[container="true"][label="Utilities/programs etc."] {
list-style-image: url('file:///F:/Other/icons/firefox/programs.png') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
}
.bookmark-item[container="true"][label="Windows Customization"] {
list-style-image: url('file:///F:/Other/icons/firefox/windows.png') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
}
.bookmark-item[container="true"][label="Daily"] {
list-style-image: url('file:///F:/Other/icons/firefox/daily.png') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
}
.bookmark-item[container="true"][label="Random"] {
list-style-image: url('file:///F:/Other/icons/firefox/random.png') !important;
-moz-image-region: rect(0px 16px 16px 0px) !important;
[/code]
and i guess [code][/code] isnt workin 
