-er:
* Stitcher: A person who stitches.
-ing:
* Stitching: The act of sewing.
-ery:
* Stitchery: The art or craft of sewing.
-work:
* Stitchwork: Work involving stitching, often referring to embroidery or needlepoint.
It's also worth noting that the word "stitch" can be used as a verb, making it possible to use verb suffixes like "-ed" (stitched) and "-ing" (stitching).