A lower back tattoo is simply a tattoo marking painted just above the buttocks, near the waistline. This kind of tattoo is getting more and more popular as this is one way to accentuate a sexy figure.
Another explanation for sporting lower back tattoos, is that people use it to emphasize physical attractiveness. Lower back tattoos are more popular in women than in men, because with the right design, the tattoo will highlight the curves of the midsection. Visually speaking, the curves of the female body converge on this point, justifying the placement of tattoos there.
Another motive to consider is that with the placing of the tattoos in that part of the body, individuals (again, especially women) will have a reason to wear clothes that specifically expose the midriff, thereby making their get-up much sexier.
The types of designs for tattoos in the lower back are abundant. In order for these tattoos to look cool, most often the designs should feature a balanced element to them; a sort of visual dualism so to speak. Common examples of this include winged designs, butterflies, vines, twin dragons, abstract designs, Asian characters, flowers, and anything that features two sides to an image.
Aside from keeping oneself attractive, lower back tattoos are a good way of showing off one's artistic tastes and are a true gauge of how freedom-loving you are.