Close the bed up with a tonneau cover. Get one of the tonneau covers that has some styling to it, like a little bit of a wing shape. I bought one for F150 at work and I got info at a truck floor mat website. Here's the page for tonneaus ... http://www.truck-and-car-floor-mats.com/tonneau-covers.html
Some bed rails and some tailgate trim and some lights might help too ... they don't cost a lot.
You can buy all these trimmings at Yahoo Stores, eBay, Amazon, etc ....