Arm modification

What are the features I can modify in a robotic arm?
How do I make the arm different from the usual?

This depends on which arm you purchase. We offer a selection of arms here:
robotshop.com/en/robotic-arms.html
For example, Lynxmotion arms are made with modular parts and can be customized:
robotshop.com/en/robotic-arm … Lynxmotion