Do you see line artifacts around your sprite tiles? Are you scaling tiled sprites or displaying them in 3D space?
Master Tile Padder is a simple tool to create the proper colored padding around each of your tiled sprites. This way, you can avoid line artifacts around your sprites as a result of filtering or mipmapping.
As a bonus, if you use NGUI, Master Tile Padder can generate an NGUI UIAtlas to go along with your tiled sprites. (Just uncomment a compiler flag!)