While you freestyle, have another person take video or photos of you as much as possible. The photographer should use lots of different angles, from far away to right up in your face. Especially right up in your face.
Whether you’re doing something interesting or not, you’re probably on camera. Cameras are everywhere, so learn to get used to them — even use them to your advantage. At first you might feel self-conscious with a camera on you. With practice you’ll soon get comfortable being filmed and it won’t disrupt your flow. Be aware that the photo or video (and you might not know which one it is!) represents an audience, so you are relating to that audience by interacting with the camera.
Have a look at the photos. Do you look uncomfortable and scared? Or do you appear dynamic, confident and larger than life? Practice making yourself look good to the camera while you freestyle. Be aware of how you present to the camera in the way you hold yourself and move while you rap. Sometimes you have to slow down long enough to create a good shot, particularly in low-light conditions. We’re not talking simply posing or mugging for the camera while ignoring your audience. You also have to remember to engage with people and look natural.
Photos of you on the mic might be seen by many people later and could define your performance or create opportunities. It might seem like this isn’t a freestyle skill, but in real world situations your freestyle skills will suffer if you don’t have this important performance practice.