Today I've started to modify the the member-cards and it wasn't until I started on a new design that warranted the close.png icon to be designed to compliment the new member-card visual. Anyway, Because I modified the position, width and height of the close.png it has some less desirable effects in other places such as the Error_Overlay and I suspect (as brogan pointed out) the poll overlay thing.
Here's the member-card I did and here are the effects on other areas so my suggestion would be right off the bat is to give the membercard it's own dedicated close image title (mclose.png perhaps) so that it doesn't effect other areas where position and sizes are thrown out of whack. Another reason is, and due to design purposes what may fit on (for example) a member card design may not fit or suit in other areas.
Screenshots below of the effects and thanks.