Installing 12v Accessory Panel

That is a fuse panel. There is no earth in that fuse panel. Doesn't look standard either

Sporto
Do you know what the two orange wires connect to in that box and elsewhere? ie, the other ends of them.
Seeing they are similar gauge to the Red FEED wire, they may be earth wiring. Hard to tell, but if 12v is present at the red and a multimeter test to the orange wires. might reveal they are negative side of the battery. It is strange the orange ones seem to have a fuse between them.
Can you test them to confirm their polarity?
The devices/system running off the current fuse panel appear to have/likely to have, their negative connections at or near the units they feed. You may know that already!
For general accessories, the additional outlets will be handy but really not suited to running a fridge, IF that is what you intend.
Pull that yellow fuse out and see if one OR both sides of that fuse link is negative side of battery.

As a professional I'm 100% positive that there are no negative wires in the picture.

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That extra fuse in the box is rated 20A (yellow body) and is a circuit unconnected to the main 12v system wiring. It is likely to be a separate feed from the tow vehicle to a 3-way fridge. In any case, it surely is not a negative circuit and therefore has no part in the search to connect the negative for the new accessory panel.

Sporto, you need to locate where the negatives associated with those visible positives are. Most likely they are all terminated to a bus or stud close to the van battery. (I assume the van does have a battery) As the visible positives are mostly red I would assume that the associated negatives will be black or maybe white. You will just have to search for them. Connect your accessory panel negatives to that same point.

Thanks everyone for the responses, it would appear that there isn’t a negative here. The orange cable is as someone suggested a fuse for the cable to the fridge.

There’s another cable that I can use for the panel which has a positive and a negative. I’m pretty sure it’s attached to the above fuse panel, so I shouldn’t need to add another fuse. I’ll check this and remove the fuse as I install the panel.