Individual site logos for multi-site accounts

I’ve shifted my personal blog to and I am working on moving some other blogs over and would prefer to have them all under one account.

Am I correct in thinking the only way to have individual site logos is to use a custom theme? This isn’t a problem, but it could maybe be something that could be configurable in the design section of each blog in the future.

On a similar note, I know it’s still early days for Mastodon support, but it would be great if each blog in a single account could have its own Mastodon username.