What are some products one could order to make a van?

If someone wants to do a do-it-yourself approach: what are some cool essential items the one could order from various websites to make a van I'd love to slowly start compiling this list and if and when the time comes it could be useful for consideration.

I'm thinking one could buy some light simple furniture and bolt it in, shelves etc.

Maybe even sink system with the pump and etc.

Maybe a bunk bed top could be used to sleep on on the bottom for storage

I bet there are hundreds of items that could be useful...

Please let's share some