Servo Heads

Servos, such as this one:
https://www.sparkfun.com/servo-generic-sub-micro-size.html

often come with different servo heads (Circle, Cross, T, L, etc.) that are used to attach the servo to the components that need to move.

This could be implemented for each servo (like a setting that lets you select which servo head you are using) or as a individual part. This would allow users to see if the heads they have are compatible with the servos and if they can connect to the part they are using.