BBCODE help - update box that is similar to quote box

[Blind Dragon]

What I would like to do is set up a bbcode

[update] content [/update]

so that when we add content to an old post it shows up in a box, similar to a quote box but with an image and different color.

I would like the background of the box to appear maybe pastel shade of yellow, with a defined image "update icon" next to the box.

Is this possible?