Good images, decent camera you have there. I'm a big fan of Nikon cameras, I shoot my gun photos primarily with a D90.
A white background would probably help, and I generally do some post-processing in
The GIMP, which is a free Photoshop work-alike. For gun photos, I do a few things to make the gun look better, especially when I have sub-optimal lighting in my photos. I did a little adjustment on one of yours, just to show what happens with it:
First, I run it through the auto white-balancer. This will fix some of the color inaccuracies in the photo. In this case, it appears to primarily have pulled out some magenta in the midtones, most likely due to some reflection off the background board.
Then, I pull the contrast and brightness up some. This pulls out the detail (such as the engraving here) and gives the image a little more striking appearance. In this case, it also pulled out the corrugation in the board that you shot the photo on, so you'll want to pick a background material with as few variations as possible.
Since guns are generally not too colorful, I'll pull the saturation of color down in the overall image, so your eye is drawn to the gun and not anything else in the background. This will also make any reflected colors and spots of irregular lighting less evident in the finished photo.
I do some professional camera work, but I'm currently hamstrung for object photography by the fact that I have no seamless background available to me. The kitchen counter is the closest thing I have, and doesn't give me room to set up my lights. To help deal with this, the above techniques done in GIMP help a lot, especially due to the fact that my kitchen has only tungsten bulbs that are not uniform in temperature. I usually have to do a little manual color adjustment at the highlight/midtone/shadow level to get them to look better. Here is an example of a recent shoot to document my AR build:
Original:
After post-processing:
Manual color adjustment is a bit involved for someone unfamiliar with lighting and photography techniques, but the simple steps above should be relatively easy to pick up with a little bit of time spent playing with these features. Anyhow, enjoy your camera!