Consider the following two images
The first one is a screenshot of the Nokia N8’s Symbian 3 home screen. I’ve changed a few things on the second image: the colour of the menu bar at the bottom and I’ve darkened couple of the widgets. I also added a sun on the weather widget, because it’s daft to have a promo-image with dark clouds (unless you really want to differentiate yourself).
Those changes are not perfect and there could always be a better theme, but the main change I did, was to change the ugly and quite old looking Nokia font to plain old Helvetica. I think this simple change would bring the whole Symbian platform back to the future designwise. The font sizes I’ve used here might not be perfect, and the themes would really need fixing too, but fixing the fonts on all new Nokia phones should be their top priority, in my opinion.