The texture should be large enough, I suppose you checked the mirror box for the x and y axis? Also, by plane, do you mean infinite plane? Did you try to map it to a cube to see if it looked better?Do you have a matching bump map to apply to the plane so it looks less flat? If not, you could create a fractal bump and see if it gets better.

bruno021 Good idea about adding a bump to the texture. I checked the x and y mirror boxes, but didn't notice any difference. Are the x and y for tiling the material? because the texture didn't tile any differently when I checked the x and y mirror boxes. What are they for? Thanks I will try and post an image tomorrow of the texture.