One of the most common fill stitches, the satin stitch covers an area with straight stitches. It works best in smaller shapes.
Chain Stitch as a Fill Stitch
Other stitches such as the chain stitch can also be used to fill shapes when they are stitched in lines next to each other. Chain fill stitches create beautiful texture.
The fishbone stitch is a beautiful stitch which is great for representing leaves and other flora. It looks fancy, but really is just a series of overlapping straight stitches.
The seed stitch is a bunch of small straight stitches that can be peppered throughout an area to fill a shape.