Ideally graphics are created specifically for use as a pattern fill so you can't see where one tile ends and another starts. Luckily CorelDRAW gives you an option to  to use with any type of pattern fill, called mirror fill. Once you load a pattern click on the mirror fill button and you'll see that any pattern can be turned into a seamless pattern.

Tip provided by Tony Severenuk, CorelDRAW Product Development team.