Yeah this is my resource pack:
www.planetminecraft.com/texture-pack/3d-crossbow-models

At the moment the structure gen is quite limited, to my knowledge it's only possible to use the three existing structure types: village, bastion, and outpost, but I might be wrong. The most important thing is that all of the files referenced exist, if they don't it won't work. The easiest way to add structures/villages is to just use the vanilla files as a template, renaming everywhere it says 'village_plains' for example to 'village_jungle'.
If you want to make a structures more common, you can probably modify the structure noise setting to make villages more common and then add a empty town centre option that's far more common than the others, allowing you to have your structures spawn frequently while keeping regular villages rare (or maybe just move pillager outposts into the village category, then make the pillager outpost type more common and use that to spawn your structures), though I haven't tested this and I'm not sure if there's a better way of doing it.
To add a single structure (not an entire village), create the files to spawn the town centre then just don't reference to any other files within it.
The best references are of course the wiki and vanilla pack, though for a lot of it, trial and error is currently the best option. Hope this helps :)