After being on the forums, and seeing that there is an issue with the quota display actually being too long for the space alloted if you have a large quota (over 1000 MB it seems) I came up with a way to dynamically generate the image. Also, I've added the functionality to enable or disable the image inside the user preferences.
There's obviously no point putting all the code and stuff here, so you can find the entire tutorial online on the forums. The link is: http://roundcubeforum.net/index.php?topic=47.0
I hope it gets added to the CVS soon, or at least added as functionality. Roundcube could really gain from it!!
~Brett Patterson Roundcube Forum Admin www.roundcubeforum.net