This free motion quilting motif is really easy to do (I guess it's a little like square stippling) and gives a really great texture. I think it suits geometric quilts really well - and you can adapt the scale to suit a whole range of areas in your quilt. I tried really hard to take photos of actual quilting step by step, but the light on my sewing machine made it really difficult to photograph well, so I think it's easier to show you with pen and paper :o)
Next, echo up the side you've just quilted a short distance, and then quilt another rectangle off to the side.
Continue echoing the first rectangle shape part of the way over the top, before quilting out horizontally and then quilting another rectangle. The important thing here is to make the horizontal line long enough that you'll be able to echo inside it without making your quilting lines too close together. Judging this distance gets easier with practice - but if you're lines are a bit close together it will get lost in the overall design anyway.
From here, I simply echo quilted down around the whole left hand of the design, and then back up and across the top of the design. As you can see, it's beginning to look quite complex, but really it is very simple to do.
Next, I quilted down the right hand side, adding a vertical rectangle along the way.
Again, more echoing around the edge of the design, adding in a couple of extra rectangles along the way.
And then echoing back across the top of the design.
To continue to build on it, I would simply echo quilt around the design, adding more rectangles along the way, and then echoing them.
The quilting on my Mario quilt ended up looking like this:
I hope this made sense - any questions please don't hesitate to ask. If you use this tutorial I would love to see the results!