A note on black holes and things they do.
Turns out trying to get them to show other things is tricky at least. First of all, they have multiple layers of skybox reflections (you can see that in some of those shots above), and that means it's very hard to actually see anything useful. As you're leaving one, you can potentially catch something somewhat clear right before the event horizon.
The event horizon is actually not the surface of the black hole (if you ever dropped into one and left you probably noticed). It's a bit further out - if the black hole has radius ~50km, the event horizon will be ballpark at ~240km. You can leave them in normal space, not in supercruise, but it takes a while because you'll need to do 300km or so at regular speeds. Other than the slow motion of event horizon passage, it's not any fancier than doing it in supercruise.
Because of the first part, I realized quickly as I was going through them, that there won't be anything special to actually see, other than some very fuzzy pictures - this is unfortunate. Another thing of note is that any star alignment you may have before you drop into them will be gone after you drop into them because the lensing effect of the center of the black hole is so strong, you get a very extreme fish-eye effect and all the stars that are overlapping the black hole before you drop in will wind up on its perimeter. You can also see that in many of the shots above which I tried to align to capture most of the O stars in the neighborhood.
In terms of looking through them, they aren't all made exactly equal. If you drop into something that has 20 solar masses, it's basically already huge, and getting around it to change the position and view takes forever. If you intend to use them to view anything, smaller ones will probably work out better. Something like 4 solar masses or below is way more convenient.
Dropping into them with a very specific vector in mind is extremely hard. They are extremely small compared to supercruise speeds - even the large ones. At minimum you're cruising at 30km / s which is more than one radius of the small ones, and barely less than that for the bigger ones, so as you approach them, the alignment will get compromised. The easiest is to just move around them after you drop in.
No black holes in that nebula seem to work in any fancy way with respect to visuals - they are all just normal black holes, and lens things the same way. They all have exclusion zones, some are very close to stars (and you can see that in those shots above, too) - this is largely inconvenient for doing anything in them, because you will get extra 10-15% of heat from the main star, and it's the whole place is blindingly bright, and on top of that you have to be careful which way you need to leave.