There is a script-fu for creating an antique look called "old photo". Sometimes you might not want all of that noise, despeckling and border. The color might not be the best either. I have found the color above is the one people tend to like the most when I do color editing. The way I tint is a simple method using layers. Do your required editing to your photo, flatten and desaturate (the color on the right). Create a new layer, set on overlay. Bucket fill with this color. If you want it darker or lighter, maybe a slightly different hue, just use the hue-sat tool. Flatten and save. Don't forget not to overwrite your original.