How do I allow a user to load a custom image into a sprite?

I would like to allow my users to CHOOSE their own character image.

How do I allow a user to LOAD a custom image into a sprite during runtime?

Example:

User_Sprite has a default image.

A user can LOAD their own image, or graphic, avatar, etc. into this User_Sprite

and play the game using their own custom image?

You use the FileChooser object to allow users to load the file from their computer and then use the load image from URL action in your player sprite object. Set up your player sprite object with all the behaviours etc that you want it to have.