...
The IdP Logo URL in metadata points to an image file on a remote server. A discovery service, for example, may rely on a visual cue (i.e., a logo) instead of or in addition to the IdP Display Name, as it helps disambiguate duplicate or similar names. Also, an IdP's consent screen may display the logo of the SP that will receive identity attributes. The logo is typically the institution's logo but may be some other institutional graphic that is readily recognizable to the institution's community members.
...