The following are plans from The English Gypsy Caravan. This book taught me a lot about layout in such a small space. There is rarely anything new under the sun and the early builders thought through the process quite thoroughly.
The figure numbers on the images are from the book. The above is a classic “Open Lot”. Essentially the simplest of the caravan designs. More sturdy than something like an American Conestoga as the walls are at least partially wood lined and there are a couple built-in cabinets. This could suit a couple people fairly well.
The “Bow Top” is a more sophisticated version of the Open Lot. More cabinetry, a small cook stove, and some shelving. Notice the corner cabinets to use the vertical space in both the above plans.
Finally, the famous Reading Wagon. This is what most people envision when they think of the gypsy caravan or wagon. Kite-shaped from the end-view, this wagon has a lot of useful indoor space. Cupboards and underseat storage are integrated and these generally have substantial chest-of-drawers built in. The later roofs had mollycrofts to allow more light and the walls were decked out with mirrors to give the illusion of spaciousness. Straight wooden walls lend themselves to hooks, pictures, or small shelves everywhere. At about ten feet long, this was and is the epitome of traveling luxury.