If your tires are huge, and/or you are lifted, this might not work...
Go find big mud flaps from a semi.
Cut them so that they cover that area in the front of the wheelwell. If you make them right, you bolt them in using the factory bolts along the top. At the bottom, where the little metal rod holds the lower edge of the sheetmetal in place, if the flap is cut just right, the bolt threads that are sticking through will hold the mudflap in place.
Had that setup on my truck for about 3 years now, and haven't ever had a problem with it coming loose. Even after driving through rain, mud, whatever, that area now stays almost entirely dry.
I'm going to do exactly the same thing for the rear of the wheelwell, since I can see that the hinge area is starting to rust. Only problem with the rear is that there aren't bolts in the same areas.
The beauty of these is that you can't even see them from anywhere except inside the wheelwell.
I've been eyeballing the newer truck wheelwells (Dodge especially) and I've been wondering if those molded plastic pieces could be utilized.