BB,
You know it is your truck, and if that is something you think would look good then go for it. The decals will have no effect of the trucks tendency to rust. The decal will actually help protect the paint, and if left on for a couple of years, you will see a difference in the paint under the decal. It should be richer in color then the rest, it was protected from the sun and didn't fad.
That said, I understand your need to seek advice. I have asked similar questions regarding my truck. It is being re-painted and I was bouncing a few ideals out to people. Your tailgate Ideal seems a little to Bold for me. I think many times less is more, with regard to decals and paint. You have taken the time to strip your truck of it's old decals and nameplates, this is great it open up the opportunity to be different. You could always try your ideal, the vinyl is not that expensive and if you don't like it, take it back off.
We are at similar places with regard to our trucks, I too have a 2nd gen, and what a new, fresh look. Like I said earlier, it is being re-painted. All the nameplates and decals have been removed. I bought '04 nameplates, "RAM 3500", "Heavy Duty", front Cummins badge, "4X4 OFF ROAD", "SLT", and "DODGE". I thought the new nameplates on the older truck would look fresh, and yet subtle, only the trained eye would pick up on it. I also have the body side molding removed and do not plan on re-installing it. I am looking for some sort of a decal or graphic to set it off, but will wait till everything is on and I see what it needs.
For you , I have been looking at RUGE exterior graphics, they are good quality graphics that come in many different styles.
www.stlinconcepts.com Has them and many other custom pieces that you may find attractive for your truck. Have you considered new Tail lights and or Clear corner lights, they sure give a different look. I plan on mixing many things in to achieve a unique look, that is my own. I have Buckstop bumpers, and Frenched in 4 LED light on the front and back to separate my Buckstop from the rest, It turned out good, and did what I wanted. You may be able to do something similar with the factory bumper, that would sure set yours apart. Many times several small changes add up to more then one big change. The loud ones seem to shout at people, which many times turns them off. The subtle changes invite people to look closer, and try and see what else has been changed.