What do you mean, "only" build muscle or change fat makeup? Makes a big difference especially, which muscles you build (fat loss though is predetermined in its distribution throughout your body and differs for each person ie you can't add/lose fat from specific parts of the body).
Over a very, very long time, your tendons and other connective tissue can thicken. So you might get thicker looking joints.
Your posture can be reshaped. Makes a big difference.
Muscles can be elongated in appearance, at least, depending on the exercises you do. Look at ballerinas (men as well as women).
I doubt you'd see much change in appearance based on bone density, the only bone changes that change appearance are malformations.