I would really like to get "Rear Wheel Covers" aka skirts for my wheels. (I have a Base Fit too.) However, they need to look good and be well-made. I think I'm not the only one who would be interested. I posted a thread on this over at fitfreak.net a while back.. are you a member?
Another (easy) thing you can add to your list is flat hubcaps - like the pizza tins or simple moon caps.
Some people drop their fits ridiculously low.. I'm not into that but I have been thinking about a front air dam. Not sure I would contemplate blocking off the grill.. but hey someone's gotta make the fit version of the aerocivic! Go for it!
Personally I tried over-inflating my stock dunlops and didn't find good results with that.
BTW, Botsapper - you used the sport model for your illustration. The sport has the spoiler (amongst other things like the sideskirts) that the base model doesn't.