I use a recipe from my breadmaker book (for standard loaf) then add or substitute ingredients. For chocolate bread, i substitute some of the flour for a few spoonfulls of instant drinking chocolate powder. If adding fruit, i just chuck some in as an extra. For banana bread, mash the banana first, and use less liquid. Basically, i make it up as i go along. Use fast acting yeast and real milk n butter for better results. Also, prove the dough first for 20 mins in a covered container by the fire. Most important - temps get very high in a box oven so use just a small fire with a few embers or the bread will burn.
Experiment! Most things work. I'm going to put lumps of real chocolate in my next one, or maybe chopped up mars bar.
Have fun!