What's the outdoor lifestyle without more gear, more stuff. These are examples of tools that can be useful when cooking with Dutch Ovens, but certainly are not required. When it comes down to it, all you really need is the oven, ingredients, and a heat source.
Protect your hands from burns from coals, ash, or sparks by wearing appropriate gloves. Some Dutch Oven manufacturers sell gloves specifically for cooking; welders gloves can also serve this purpose.
Take a look at the Recipes section for more information about what to cook in a dutch oven. Check out these resources for more information on equipment and tools:
Aluminum flashing shield
Cold temperatures and wind can have negative effects on your heat, especially wind. Wind will move the heat off your oven(s), increasing cooking time, and requiring more coals than normal. Windows shields can be logs placed up wind from your ovens, to aluminum/steel sheets wrapped around the ovens, to shields built in to tables. The pictured solution is lightweight, easy to install, and easy to store flat and out of the way.
A tool used to start burning charcoal. Useful for keeping the coals together, which speeds the lighting process.
Also helps with pouring coals.
Simple kitchen tongs to move coals. If needed, you can also use them to lift or rotate a lid.
When you remove the lid to remove coals and ash, you're going to place it back on the oven with fresh coals. Lay that lid on the ground, you may end up with unwanted dirt, debris, or insects in your food. You can use a trivet, specifically made lid rests, or even rocks. If you choose to use rocks, consider whether a wet or sandstone (layered) rock will split or explore from heat.
A helpful project for Boy Scouts would be to use rebar to weld lid rests. The Scout benefits with a project for the Welding merit badge and the unit gets equipment.
Something placed under a pan or cooking food inside the oven. It is designed to keep food off the bottom of the oven to prevent burning and even cooking. Examples include cooling racks used for cookies/cakes, or aluminum foil twisted into an S-shape. Some cooks use rocks or stones, but the wrong kind of rock can heat and explode in your oven. Not a desired event in your campsite.