All right, let’s see what we can do to get you squared away and hopefully offer some helpful clarification. 
Apologies in advance for the length, but I’ll do my best to leave few-to-no stones left unturned
I’m not aware of there being any inherent server issues, per se, or at least have not come across anyone having shared that they’ve experienced any issues more than maybe once or twice in many months. We’ll just start there, as an opening salvo
That being said, let’s see what we can do to hopefully clear up any confusion and or help in understanding:
First, in a broad sense, the answer is sort of that it ‘depends.’ We do have agreements with various other organizations, the terms and specifics of which vary.
Sometimes we get cart blanche to share lots and lots of stuff, sometimes we get specific permissions to only share a small handful of images, etc. (or, in some cases we don’t get permission at all and so, perhaps obviously, we can’t/won’t use that media in the deck).
It can also be the case that we are able to directly share some media, and an organization may, separately, decide to additionally provide additional material (or not) elsewhere. This isn’t common, though it’s not historically without precedent. As with anything, the specifics vary. You can find a bit more information here from our end, if it’s helpful:
Separately, if you are ever curious about what media is carried by AnkiHub for a particular note or card you can always check this by clicking the ‘View on AnkiHub’ button from within Anki and this will show you the card as it exists on the AnkiHub servers:
If there is media stored for a particular field, on the AnkiHub side, it will be visible from the resulting page once you click this button (provided you are logged in, of course).
If that page shows media for a given field, then AnkiHub has that media (and can sync it to your local collection). If that page does not show media for a given field, then AnkiHub does not have that media (and cannot, thus, sync it to your local collection). If you’re ever curious about a specific note or card this is the easiest way to verify if something is actually meant to be there, and/or if you’re actually missing anything.
Second, to clear up any potential confusion (not that there is any, just for due diligence): ‘resetting local changes’ will reset your notes and media to what is stored on the AnkiHub servers. Worth noting: it will not affect any review history or learning progress.
So, if you have media in an unprotected field that is not held on AnkiHub’s servers, resetting local changes may very well remove, adjust, or overwrite that media.
From there:
- If you have media in an unprotected field and it is the same media that is on AnkiHub, it will remain essentially unchanged.
- If the field is protected, resetting local changes will have no effect on that field either way and it will remain however you had it beforehand (any edits, or changes, you may have made will have been preserved).
Third, as far as Physeo, we have permissions to share some of their images though it may be that for some of their offerings you’ll separately need to have a paid membership. You might log into their website and see what’s what, and what they offer, and it may be that some of the media they offer is outside the bounds of what is available on the AnkiHub servers.
And, lastly, this may be part of what hopefully ties it all together: some fields on AnkiHub start out protected by default (FA, BnB, others). This is by design, as those fields are largely intended for personal use and are not typically modified by AnkiHub (we don’t, for example, have BnB media to share in that field and so it’s entirely protected as it’s only designed for individual personal use).
Owing to the way these fields work, if protected they just look blank. But, because of an oddity of how Anki handles those fields there is actually something in that field. But that something is essentially a URL container that points back at Anki’s media folder (it is, essentially, Anki pointing at itself). There are weird reasons why this is, but essentially it’s a quirk of how Anki and AnkiHub interact and one of those weird visages of a system that got built on grandfathered versions of itself. There is no media there, just a URL-pointer linking back to its own media folder.
So, let’s take the FA field for example: it is protected by default. There’s nothing in that field on the AnkiHub side. Basically empty.
But, it does have those little URL pointers in the HTML code for that field so that, if you were to put in a screenshot or something yourself, that field will point to the appropriate location in your own media folder. If the field is protected, it shows up as blank. If you unprotect that field, however, AnkiHub thinks that it should start looking for something and, since there’s nothing there, you just get a broken image icon (bc the URL pointer is pointing at nothing, essentially, and having come up empty-handed it returns a broken image icon bc it thinks something is broken or missing).
Thus, some fields are protected by default and this is by design rather than being a server issue of any kind. As long as those fields, that are intended to be protected, stay protected, you should be fine and nothing is amiss (typically this also indicates that AnkiHub does not directly have any media to provide for that field). If you unprotect that field, though, you may see those broken pointers and come under the impression that there is missing media though that is not the case.
Just about a novella, at this point, though this is about as full-throated an explanation as you’re likely to get short of a developer or a TED Talk. 
Super TL; DR: if a field is protected by default, there’s nothing there and you’re not ‘missing’ anything (at least from the AnkiHub side). Unprotecting that field may return broken image icons, but this is an artifact (hence why the field is protected by default). Separately, if a company decides to offer their media independently, you may be able to find a media package or similar, outside of AnkiHub. If you just want those broken icons to disappear, you can protect the field and that’s that.
Hopefully that helps clear up a few things, such as I’m able. If you have any other specific questions, though, please send them my way and I’ll do my best to be of service.