Which elements of the frontpage can be customized per site?

Question

What are various things which can be added to the frontpage of a single site to include some information to the users? (As opposed to stuff which is displayed on all Stack Exchange sites.)

So far I have seen:

• A banner on Medical Sciences. (Two paragraphs : "Do not share personal medical information, medical history or any other specific details about a person's medical symptoms, condition.... Full disclaimer and more information about this site here.")
• There is a similar disclaimer also on Law Stack Exchange. ("Law Stack Exchange is for educational purposes only and is not a substitute for individualized advice from a qualified legal practitioner. Communications on Law Stack Exchange are not privileged communications and do not create an attorney-client relationship.")
• A banner on Christianity. ("Like any library, Christianity Stack Exchange offers great information, but does not offer personalized advice, and does not take the place of seeking such advice from your pastor, priest, or other trustworthy counselor.") This one is a bit different from Law and Medical Science - since it doesn't link to site/help/disclaimer. It seems that it was inspired by a similar banner on Mi Yodeya.
• As a temporary change, a small banner congratulating to the 10th anniversary was shown on some sites: When is the "happy anniversary" banner displayed?
• There is a related discussion here: Wanted: A standard way for a site to have a prominent professional advice disclaimer. But since that post is from 2011, I assume that some of the information given there might be outdate.

In all cases mentioned above, it was something located in a banner in the right sidebar.

Main question. Is this banner the place where a site can include some information different from the default setup? If users from some community want to include something here, is the right process to post a feature request on their per-site-meta?

Apart from that, other things that I have seen different on some sites from others that I saw are:

• Omitting HNQs from the frontpage - although there are only a few sites modified like this: Which sites show recent badges on the frontpage?
• Removing some badges from the list of recently awarded badges. See also: Remove 'Autobiographer' from Recent Badges

Additional question. What other things on the front page can be customized for some Stack Exchange site?

Answer 1

As with almost anything, reaching community consensus on your per-site meta, and then tagging that post with [status-review] by a moderator is the way to go to get something done by the CM's.

If it is an already pre-existing element in the networks design, as you've listed above, I see no reason why it couldn't be switched on to any given site when that site has described an appropriate use-case for the feature. It might be that it would take some work by a developer, instead of something the CM's could do themselves. For that reason it could get declined by CM's, but I feel that that would be a case-by-case judgement on how "valuable" the addition is to a given site, and how much work it would actually take a dev to make the changes needed.