If you are using gimp you should be able to put the tile image in your pattern folder and then just do a layer bucket fill using that pattern. If the scale of the image "leaves" is off you may have to work with scaling the original tile so that the leaves on it are the right size, then save it at that size to you pattern file. Also if your tileable texture is not that tileable (leaves big ugly seams) get RobA's "better seamless tiles" script, it is much better than the one that comes with gimp.