Noteably, there are now numerous mounds of sand.
(not sure what is happening here, though one of the mounds appears to be stored inside a bunker silo..)

Imagery: Maxar Premium

Missing possible service way and parking (capacity 2, or 3)
Would extend from existing service way to the south.
A car seems also visible on Esri Clarity to the west of this note.

Source: Esri

Missing possible paths, survey needed.

https://www.mapillary.com/app/?pKey=1114040119077804&focus=photo

Missing benches, picnic table, life ring(s) around the water not detected by Mapillary. See Mapillary 2017. Among others

https://www.mapillary.com/app/?pKey=4141373485926378&focus=photo

Missing two structures north/south of here; local knowledge needed
See Geograph linked at the bottom for more details
May sometimes be underwater.
Not visible on Esri Clarity, nor British War Office layer.

Suggested tags:

wikimedia_commons=File:The Duck Pond, Kilkenny Castle grounds - geograph.org.uk - 3361068.jpg

Sources

Aerials are regular Esri, Maxar Premium, Bing, Mapbox

Mapillary

There are plenty of pictures from around this pond. They're especially visible on the 360 ones of course. See e.g.
https://www.mapillary.com/app/?pKey=5467349640005322&focus=photo

Wikimedia Commons

Similar image to the Mapillary example linked above, but from the other side of the pond.

https://commons.wikimedia.org/wiki/File:The_Duck_Pond,_Kilkenny_Castle_grounds_-_geograph.org.uk_-_3361068.jpg

Geograph (use for reference only!)

The other Geograph image seems not to be on Commons as far as I can see. This one has more details however:

https://www.geograph.ie/photo/6625167

Missing details, local knowledge needed.
"Security"

Source (use for reference only!);
See map at https://kilkennycastle.ie/about/accessibility/

Missing path, survey needed.

https://www.mapillary.com/app/?pKey=5476438932431329&focus=photo

Missing memorials or similar and inscriptions, survey needed.

https://www.mapillary.com/app/?pKey=132787242177769&focus=photo

Note to self: Correct way geometry

Missing fire hydrant.

Mapillary 28-08-2018 by zors1843
https://www.mapillary.com/app/?pKey=539323450807337&focus=photo