You can click on the image to upload a new one. Notice that there's no name or location specified. Do you wonder where it's stored? If you were like me, you'd just say "doesn't matter, Salesforce handles it". That's all good and nice, until... you need to deploy the shiny new app. If you just include the CustomApplication in the package.xml, like any good developer would, an error like this would crop up.
applications/LightningSalesConsole.app -- Error: In field: logo - no ContentAsset named hack_Logo3kb2 found
There's the image storage you never knew. It's called ContentAsset, which you need to bring along with your deployment. Simply include this in package.xml:
The question is, how do I find the ContentAsset name easily (without having to open up my .app file or waiting for the error)?