It would be harder to hide the box, at least without using custom JS. But you should be able to use the custom toggle feature to have the image as the toggle switch. Perhaps try something like this.

[[File:LooBoxImage.png|link=|class=mw-customtoggle-1]]
<div class="mw-collapsible mw-collapsed" id="mw-customtoggle-1"><gallery>
Item1.png|Item 1
Item2.png|Item 2
Item3.png|Item 3
Item4.png|Item 4
</gallery></div>

Note that if you are going to have more than one box on the same page, then they will each need to have their own unique "mw-customtoggle-".

Actually, if you want the box to be opened just once and then just stay open, something like this might work.

<div class="mw-collapsible" id="mw-customtoggle-box1box">[[File:LooBoxImage.png|link=|class=mw-customtoggle-box1box mw-customtoggle-box1items]]</div>
<div class="mw-collapsible mw-collapsed" id="mw-customtoggle-box1items"><gallery>
Item1.png|Item 1
Item2.png|Item 2
Item3.png|Item 3
Item4.png|Item 4
</gallery></div>

I tried something here:

User:Oot42/Sandbox-4?oldid=3860627

(edit: updated version)

@Andrewds1021:

Did you test your solutions?

They both seem not to work.

I did not test it since I have done something similar before but without images. If it didn't work when you tested it, then I would guess either it is because of the image or something changed with how the collapsing is done now.

Okay, found the issue with my proposed solution. This one should work fine since I actually tested it this time.

<div class="mw-collapsible" id="mw-customcollapsible-box1box">[[File:Example1.png|link=|class=mw-customtoggle-box1box mw-customtoggle-box1items]]</div>
<div class="mw-collapsible mw-collapsed" id="mw-customcollapsible-box1items"><gallery>
Example1.png|Item 1
Example2.png|Item 2
Example3.png|Item 3
Example4.png|Item 4
</gallery></div>

The issue was that the ID for the collapsing content needs to be "mw-customcollapsible-" not "mw-customtoggle-". That is what I get for letting my wikitext skills get rusty.

Both your solutions work perfectly fine! Thank you so much for your help!