I don't believe a gun rack is so specialized in nature as to present a challenge for a competent trim carpenter; in fact, it is likely that a trim carpenter may be a shooter/sporstman himself and has already given this a lot of thought. The challenge is coming up with a design that is both efficient and consistent with the decor of the room. If you Google "gun rack" and then click "Images," you'll see hundreds of ideas, most of which I bet will not suit your needs. But they're ideas for storage nonetheless, and maybe can be adapted to your room. Most of these store-bought racks I find very clumsy looking and inefficient, by the way.
When I designed the racks for my room, I first visited the NRA's National Fireams Museum in Washington, D.C. I figured they, if anybody, should know how to display a firearm---and I was right. I came away from there with plenty of ideas that I put on paper and adapted to my room. One of the most versatile was the idea of anodized (or painted, as you prefer)"C" channel, 3/4" X 1/2", which is mounted vertically on the wall. 1/4"-20 threaded screws slide inside the channel, permitting rapid adjustment to accomodate any size or shape of firearm. This aluminum track is available on Ebay in various lengths, but you're on your own to design and make the chocks to hold the firearm---again, I stole a lot of ideas from the Museum, Internet, and various sporting goods shops.
You might also consider visiting Tap Plastic's website to peruse the use of Plexiglas and other acrylics. They have some excellent tutorials on how to bend and join acrylics, and it may appeal to your creative side.
