My latest, and largest, is an eagle on my chest that spreads across from shoulder to shoulder, 27.8 inches and, from just above the sternum to the top of my abdomen, about ten inches. I'm very tall, 6'5" and very, very long armed-in a shirt, 37-39. I had long wanted an eagle but backed off from the stylized, uber patriotic ones as, personally, I wanted a more accurate rendition of a magnficent bird. (As it was applied over several sittings, a friend commented that it was lucky I was no fan of the turkey vulture.) What I learned from this, and from Josh, my tat guy, is that it really is necessary to consider what you want and where you want it simultaneously. I've taken several designs to him that he's rejected as no suitable place could be found on me. Sometimes this is occasioned by a tat already in place or just that given the curved nature of the human body it would seem strange to have it go around. On the other hand, a slice from Dali's "The Persistence of Memory" was custom painted to go over the back side of a shoulder and a bit further down. I enjoy my tattoos and, at a very late age-68-have started my collection. The interesting thing is that, given my age, I'm not defined by my ink as will sometimes happen with the young. I am my own person and, when I stand to lecture, even if some or all of a creation shows, it's my intellect that is revealed. Too, when I get to the morturary, my ink will be fresh and bright. The take away is that a great design can be ruined by placement or crowding. If it doesn't fit, then that's it as far as that tattoo for you.
Size and placement are always crucial to a successful tat. Placement is usually the first thing I consider when I'm looking for fresh ink. Once I've settled on where, then I look at what and how big.