I'm looking for a way to make a precise form for baking bread in it. I have a gas-powered oven at home and I'd like to find an easy to shape material that could be used to make a complex form or parts of it that can be assembled and will not deform from heat or the pressure of dough. I don't think I can manage precisely shaping something as hard as metal pans, but perhaps wooded planks with some preparation could work?
With such tiny details, wood will give you trouble - even with very careful seasoning and greasing you will probably not be able to get the cake to release properly and without ripping the details apart.
My first suggestion would be stoneware / clay:
You can easily shape it including details and after being glazed and burned it will be ready to use. Either find a potter do do it for you (even modeling it off a positive shape you supply) or do it yourself, you just have to find a kiln you can use.
Shaped stoneware molds have been in use for centuries, here are two random examples showing rather fine details:
Or find someone who can make it in metal, but your sheets must be a) thick enough to allow for thinning at the imprints and b) made to resist warping - that's definetively a job for a professional.
A popular way of producing custom molds is to make your own silicone. For that, you buy a bottle of silicone sealant, and knead it in a bowl of cornstarch until it gets a workable consistency. It handles much like pasta dough at that point.
Use a standard rolling pin to roll out a sheet of it, and press details into it using whatever tools you can think of. If you need many repetitions of the same shape, it is best to first make a positive of the shape from something sufficiently firm, and then press it into the sheet multiple times, to produce something like the silicone molds for cake decoration pieces.
If you don't want just dimples in a flat sheet, but a loaflike shape, you can line a bowl or pan of roughly your desired shape with it, and make the surface details on the inner surface.
After you have finished forming, let it cure at room temperature for 2-3 days before using. As an upside, it is very easy to release food from it.
Make sure to use food grade silicone, not just a random one from the hardware store.