The Italian flag is a basic yet beautiful design---three equal-sized bars, a green bar on the hoist side (left side), a white bar in the middle, and a red bar on the right side. But if you want your tattoo to stand out, remember that a simple rectangular design of the flag will look cheap and unimpressive. The perfect geometry of the actual flag will not translate well, especially if the tattoo is on a part of your body that will change shape over time (the shoulder, arms, neck, chest, etc.).
This problem can be solved in several ways. If you are interested in just the flag design itself, your tattoo will look much more impressive if the image is designed so that the flag looks as if it is blowing in the wind. Another way to retain the flag's design but change the shape would be to use an elongated pentagonal shape, much like the crest worn on the uniforms of the Italian football (soccer) team. Although this shape is geometrically similar to the rectangular flag itself, the more intricate design worn on the chests of Italian footballers allows it to show up bolder and more intricate.
If you're looking to add an Italian flag to a sleeve collage or other high-traffic area and you need a background color to help the flag mix well with your other tattoos, a good base color to use would be sky blue (azzurro). This is the color worn by Italian national sports teams to honor the official color of the Royal House of the Kingdom of Italy. In a more aesthetic sense, the blue provides a great base and accents the colors of the flag.
If you're looking for a design that mixes other elements in with the Italian flag, there are several culturally appropriate options.
One of the more popular options is the country's geographical design, which is a unique shape in itself. A good design may incorporate the country's shape by having the flag wrapped around a solid-colored or shaded image of the Italian "boot." Another option would be to outline the country's shape in a bold black design and simply fill in the design with the image of the flag stretched appropriately to accommodate the country's shape.
Because of the rich religious history of Italy, a cross may be the perfect thing to accompany the Italian flag in your design. You might decorate an elaborately designed cross with an Italian flag draped over the arms of the cross---this would be an appropriate color scheme as well because the green and red would be on either side of the cross with the white bar in the middle. A cross with the pentagonal crest design hanging in the middle would be another option.
You can be as specific as you want. The Italian flag can be accentuated with any number of culturally appropriate designs, from football to cuisine to a portion of the country's beautiful landscape.