Nice way to make noise seamless (without tampering with the noise generator)
If you can't change the textures, I see 2 possibilities:


Use mirrored repeat on the noise textures so they tile seamlessly.  (taken from here)
Do like Gimp does (or many other alternatives) and create tilable versions of the noise textures. The idea is to blend the left and right, and bottom and top edges together in pairs. Here's how to do it in an image editor: translate the image by 1/2 in both axis so the corners are in the middle. Blur, smudge, etc. to remove the seams. Revert the translation.


 

Keep in mind that the randomness and quality of the noise will of course be affected by either technique.