I have a very simple question that I can't seem to get clarification on. When opening a wallet on Yoroi it shows the pool you are delegating to if you are delegating to a pool. The pool has a default icon (See screenshot below) How do stake pool operators change the icon to a custom icon?
It is related to PoolMetaData.json as you said, inside the file you can add the link to the extended version of it where you can add different things, for example a description of your hardware, social networks of your pool, and many other things included a pool logo.
You can find an example version of it here
Once you have edited the file, added the things that you want and uploaded the file on your website, you can link it with your pool by adding this line to the existing poolMetaData.json that you have:
After that you need to recalculate the hash of the basic metaData file, resubmit the pool registration certificate and the delegation certificate. Here you can find the guide to resubmit the poolMetaData and its hash file.
Note that after that, in staking section of wallets, your pool will be seen as "unknown" until ADAPools will sync again (every 4 hours).