As I have stated in previous posts, many people get confused about what quilting is. They picture beautiful patchwork blankets (which are of course called "quilts"), and think that patchwork is quilting. In fact, quilting is the sewing of multiple layers of sandwiched fabric together. The traditional quilts that you may think of are usually one layer of patchwork, a layer of flat, insulating batting (stuffing), and then a "backing layer" (the underside of your quilt). Some quilts have all three of these layers, while others are only made with a top and bottom layer. In the amazing quilting technique of "Trapunto," the stuffing is bunched and molded into pockets that help the sewer create sculptural effect, an entire fabric bas-relief.
I like to make my eyes out of felt. Felt is a sturdy fabric that does not tend to fray when you use scraps in detail work, and it comes in a wide variety of colors.
The layers of different colors of felt create a slightly rounded dome--a cross between a two-dimensional and three-dimensional eye. I use black felt as my base layer, white as the "white of the eye" (surprise), and then I get more creative with the iris and pupil.
I recommend cutting out all of your layers before stitching, so that you can see the overall size and effect while you can still tweak everything. Make sure to leave a border of your base layer around your eye design, so that you can easily stitch your completed eyes to your plushie. This border will also create a nice, bold eye border on your finished plushie face.
Try to use a matching thread color for each layer. The eyes are still clearly hand-stitched, but the stitches won't distract from the overall eye design.
And voila, you have a quilted eye:
When attaching your eyes to your plushie, try to stitch at a bit of a diagonal, stitching from the outside of the eye and sliding the needle between the layers of fabric a bit, to tack a wider section of the felt eye to the plushie head. These plushies may see some wear and tear, after all, and you don't want to worry about the eyes tearing off.
The larger the eye, the more detail and layers you can include. But this eye technique looks great either way, and can give your plushie a nice bit of flair. This is also a nice, compact bit of crafting that you can carry around with you from place to place, and it can turn your scraps into something functional.
Have fun crafting!