To make them a seamless tile, select all and use the Simple filter choose Quick Tile... this is a free filter

The free filters can be downloaded here http://www.btinternet.com/~cateran/simple/

I use the Quick Tile a lot. It works best on a square canvas... meaning the width is the same as the height.

You might try this on a canvas 350x350 this is a good size. Have Fun...