Here are some rough ideas for mine. The spare is going in front on the tongue. Inside the front section that is divided I will have water tank, battery, spot for firewood, and other assorted heavy items that will be fairly permanent to the trailer. Then build a platform on each side that is just shy of being level with the bottom of the side doors. It will have some tiedown points and netting and will be used to hold sleeping bags, luggage, and other light items that will be unloaded every night. The platforms will be hinged so I can access the battery, water tank and firewood under them.
The back section, which is from the divider back, is open all the way across. It will be the kitchen. It will have a stove, icebox(fridge once I get the money), grub box, and propane tanks. Plan on having it on a slider so I can slide it out for easy access and weight distribution. Will probably have the kitchen area built up fairly high for "cupboards" etc. Will have to watch my weights carefully, especially behind the axle. Anyway, anyone else have any words of wisdom to add.
Oh I forgot. I have two OZ5 tents that will go in there somewhere too. I also plan on having an awning on the back over the kitchen area and on one of the side doors. I would also like to be able to put some mountain bikes and/or dirtbikes on it too, not sure how or where or if its even feasible at this point in its build.