The nine-square grid design (or tic-tac-toe board!) is a framework you'll see me use a lot my pages. It's simple, linear, and always results in a perfectly balanced page. And while it is ideal for square elements (especially if they're sized 3" x 3"), you can also break out of the box and use a variety of shapes within this structure.
On this layout, I've used the 9-square framework, but filled several of the squares with small circle shapes, cut from my paper and cardstocks. The circles add motion and energy to the page without overwhelming it, because they are contained with a small, defined area.
So just because you start with a grid design doesn't mean you have to keep all your elements square. Try filling the grid with hearts, stars, hexagons or circles to pack a design punch.