Personally, I think it would take too much effort to fix the faint outline or halo around the image one pixel at a time. This texture is far from “seamless.” If your bitmap editor has a seamless tile feature that allows you to mirror the image around one or two axes or overlap adjacent tiles, you may be able to fix your image satisfactorily. Otherwise, as Dave said, go shopping some more.
You should seriously consider equipping yourself to make your own seamless tiling textures from photos. With a suitable bitmap editing application (aka “paint” program, aka photo editor) You should be able to bring in an image and quickly crop it and adjuxt to fit up against itself and test out its tiling ability.
There are oodles of photos out there (e.g., via Google Image). You can just grab one that appears to be in the public domain, bring it into your bitmap edior, and turn it into a smoothly repeating tile, which you can then import into SU and make it a material. You can even change its color.
-Gully