To be fair it is in Style properties basic options, where you would set your forum logo that displays in the header. However a serach in ACP for logo does not return that result. You have to search for metadata logo and I'm sure that is less intuitive than searching for logo.
By default, Facebook uses the Metadata logo URL but you can edit the metadata_macros template to set it to something else. I had set it to the 512x512 one for Twitter, but at some point during troubleshooting changed it to the 192 one, which is apparently too small for Facebook.
What about metadata for add-ons? Is that going to be per add-on (as in reaching out to vendor)? For example, if someone goes to my support page which uses @Naz (Nixfifty?) Tickets add-on ... it says "Create support ticket in.." where we'd rather have it say something a little different.
Just a thought. I haven't deep dived all throughout my site, but thought it was worth a question.