Had a brief look but can't get the background (grey) opacity changed.. I've added a screenshot - I'd like them clear (or semi) like the weather widget.
Anyone else given this a shot? When I get computer access later I'll have a better look.
There are a few plugins in system/library/WeeAppPlugins. I don't know if any of the tweaks in your screen shot will be there, but that's also where the Weather Widget background is (the Social App plugin too).
If you're using Winterboard, there's also a Translucent Notification Center theme in Cydia that will clear the background shadow images for a number of different widgets.