The best textures are ones where they cover a large area and are random. Seamless textures where one edge wraps to map to the opposite edge creates an obvious pattern if they spread to repeat over a large area. To solve this I would like to define an array of x textures, each having the same edges so that any one could be seamlessly placed next to any other. The render then randomly mixes the order of the textures when repeating over a large area to make it look really natural.
Specifically this would be for brick walls, gravels, wood, flooring...etc. (I can't actually think on a texture application where this wouldn't produce better results.) The only down side is that there are no current textures like this (that I know of) so you would need to start a new library... but this could be a USP to ship with the product.