By not using the config service.
Your use case doesn’t fit well with the config service due to the limits on the config service.
And whilst sure an image is just a string blob at the end of the day it really doesn’t align well with being in the config service
The Config Service can only hold 5kb of data. And thats not gonna give you a lot of space for a good sized image
See the related API function on the config service Reference | Twitch Developers
The segment is limited to 5 KB.