Although it may sound obvious, including photographing everything, walk around the outside of the van recording or writing down any additional equipment that may be there whether damaged or not. Solar panels that are not removable and ancillary equipment, Gaslow (if fitted) All or as much of the contents of any external lockers and bike-racks etc. Some of these items may 'walk' before the claim is concluded. The same also goes for internal equipment and treasures.
The insurance company may provide boxes or you could obtain boxes to store as many items as you can.
Receipts can bring back full value but without receipts you may only obtain a percentage of their worth.
All the very best!