Change/Update Image asset from external URL via Script

Hi, im complete new to Anthais.
I would like to setup a System where a script on systemboot connect to a URL and copy a IMG file from an extern webserver to the Anthais system.
Than i would like to save the IMG file over the existing img witch i set up for display in Anthias Asset Manager so that it gets updatet every systemboot without doing everything by hand.

I installed Anthias manually so i can log into console, i can write a script for the copy action but i have no clue about Docker and were Docker save Assets and if i can overwrite these files?

Can someon help me out with informations about that?

Thank you very much!!