I love me some ect.
This is something that is on the todo list, as someone else asked for this as well a while back. In the mean time you can fix this by adding your own css in the shoutbox header (see admin panel). The code for that is:
If you selected the "complete" shoutbox during registration, there is already some custom css in the header, just replace it with this one:Quote<style type='text/css'>
If there is no custom css in the header, you can use this:Quote<style type='text/css'>
What this does is make the body that surrounds the shoutbox transparent, not the shoutbox itself. If you want other elements of the shoutbox transparent, then you need to add additional css values for other elements like .cell1, .cell2, .cell3, .cell3b, .tablebg, .table2. You can experiment with the elements to see what works best for you.