It is definitely an outdated, even laughable idea that female back tattoos are for only the "loose" ladies and particularly thinking of the lower back tattoo as a "tramp stamp". It is extremely close minded to think that an attractive woman with a back tattoo must be immoral and unsatisfied. It's very much the other way as a woman who is strong, independent and fashionable is one who would strongly consider a female back tattoo.
There are certainly a few fantastic reasons for desiring a female back tattoo in addition to fashion. Regardless of what part of the back you choose to have a tattoo inked you have the ability to cover it when appropriate such as many workplaces that still require tattoos to be covered. Also a design in this area will highlight the natural curves and shapes of a woman, predominantly the lower back or tailbone area. When a woman chooses to wear clothing that will allow their lower back tattoo to be visible it gives the impression of sensuality that other tattoos fail to accomplish.
There also is the upper back tattoo which is highly popular. These tattoos can range form a simple small and delicate design such as a flower to a large and elaborate design. Similar to the lower back tattoo a high back tattoo should be placed in a way that it can be covered when appropriate. However the upper back tattoo may be more difficult to cover up when formal dress wear is common. A gown for example would usually be lower cut around the upper back making it difficult to cover your design. You might consider a smaller design that would better blend with this type of formal wear and actually add to the attractiveness of your look. It does seem that the social bias of tattoos is fading and therefore some female back designs might be admired in this setting.
On the other hand outdoor wear such as bathing suits and tank tops and other casual wear would expose your design. This setting though would be one that a larger tattoo might be greatly accepted and admired. It is a good opportunity for a woman to show her strength and independence. Men like strong, independent and confident women and think of them as sexy.
Great is this art and the wide array of designs from simple to complex allows you many possibilities to be imaginative with your design. Online galleries offer a seemingly limitless collection of suggestions and ideas. So it is good to do your research and make sure you will be satisfied, and can live with this tattoo the rest of your life. Do this by designing your art to your personality and I know you will be happy with your tattoo.
Starting from the top down, here is what is known to be just a partial list of Pink's tattoos: 
