I am not sure there really is much of a market for it and a lot of places on the internet already offer a lot for free.
But if I were to need to buy a texture pack, then it would have to be a lot of realworld textures, not those that looks like they were made using a texture generation tool. And it would have to be as complete as possible within the choosen theme.
So for instance a forest pack would be a large selection of leaves, tree trunks, branch surface and so on. An urban pack would be various concrete walls, metal beams, windows, doors, entrances, brick walls, road surfaces, and so on.
I have no idea about how something like that would be priced, but those are the things that I would expect, should I have to pay for it.
But if I were to need to buy a texture pack, then it would have to be a lot of realworld textures, not those that looks like they were made using a texture generation tool. And it would have to be as complete as possible within the choosen theme.
So for instance a forest pack would be a large selection of leaves, tree trunks, branch surface and so on. An urban pack would be various concrete walls, metal beams, windows, doors, entrances, brick walls, road surfaces, and so on.
I have no idea about how something like that would be priced, but those are the things that I would expect, should I have to pay for it.