Ear tattoos are becoming a popular trend, especially with women today since you can cover them if you have long hair and there just isn't a huge area to be worked on so it is a pretty fast process compared to other areas of the body.
I am classifying "ear" tattoos as any actually on the ear or right behind the ear. I've seen more photos of the behind the ear style but more of the actual ear/ear lobe are starting to pop up. These are pretty interesting in the fact that for such a small area there is a big range of choices. As you can see in the photos, you can go from Gothic to feminine with no problems.
As you can see your choices are very open you just need to decide if you want it where it can be seen no matter what or if you want to be able to cover the tattoo with your hair. Also, I have read that the skin on the ear continues to grow quickly and you may need to do touch up sessions more often then anywhere else. Keep this matters in mind when you are thinking about ear tattoos. You may want to check with your employer or at least think about whether or not this will effect your job status prior to getting this type of tattoo. Better safe than sorry.