With special thanks to the original RostaP's https://www.printables.com/model/152592-honeycomb-storage-wall and along with Christian Long's https://www.printables.com/model/558180-honeycomb-wall-large-panel-format-edge-corners
In order for you to make use of these files you need to print the following; I'll use a 3x3 as an example:
I took it a bit further and modified the edge stl's so they better fit with the standard wall-honeycomb-part.stl of RostaP's.
This means that it can support the standard wall honeycomb part in multiples of 2x2 up to any.
There are two files, one smaller which fits the 3x3 honeycomb grid using Christan's edge files. The other you can see in one of the included photos, at the top is Christian's original, the second is the new piece 7 hexagons long which from the other picture can see it ties in nicely on the 3x3 grid any upwards as it's the same length as the wall-honeycomb-part from RostaP's.
Printed on my P1S, 0.2 layer height. 5% infill.
The author remixed this model.
Taken the heavy influence from this file and modified it to fit the standard https://www.printables.com/model/152592-honeycomb-storage-wall: wall-honeycomb-part
This makes it better to print direct and fit together, if you want to do a greater than 2x2 grid, built for a 3x3 hexagon grid but would scale.