It would be handy if the Shell component supported setting a favicon.
eg. same as how the stylesheet can be filled in from the Shell component -
<link rel="shortcut icon" type="image/x-icon" href="/favicon.ico" />
I'd expect to be able to have
<private-asset name="favicon" resource-path="/images/favicon.ico"/>
<span jwcid="@Shell" favicon="ognl:assets.favicon" title="MyCorp Customer Login">
If this has merit, I'll submit a patch. If there is some elegant way I've overlooked, please let me know.