Multiple Tiling Textures
Is it not possible to allow the user to specify more than one texture tile for a material and then have the rendering engine randomly tile these to create a non-repeating texture?
The only constraint would be that the edges would always have to match. I realise that this would still leave the possibility of a repeating pattern, but there are planty of textures (e.g boarding, masonry, etc.) where the material has natural joints and making sure that these coincide with tile edges would overcome this problem.