Here I have an image found randomly, somewhere on the internet.
But when tiled it has obvious seams
The Dink way to solve this problem is to take the center of the tile
And use it to create a blended seam around the edges of the tile
Cross-fading the center of the image to the outer edges will result in a nice, smooth seam like so:
I've even made a plugin for PaintDotNet users that will automate this process. You can find it here: http://forums.getpaint.net/index.php?/topic/106712-blend-seams-for-smoothing-out-pesky-seams-on-textures/