Since GM:S, there's a native method of loading sprites from remotesources like an URL. Cloud Asset Manager uses these new functions to implement an easy and manageable system to load sprites, spritesheets and backgrounds from the web in your projects. Cloud Asset Manager instantiates an object that stores sprites and backgrounds and lets you easily retrieve them using their assigned names, along with checking if said sprite exists, and returning errors when a remote sprite isn't available.
Comes with an example project where you can add, delete and switch sprites and background, in case the extension by itself isn't descriptive enough.
End User Licence Agreement (EULA).