The first bag I made was using the linked pattern above. After that I started experimenting with variations including:

• inner pocket for keys, phone, etc.
• substituting seed stitch for garter stitch
• making a rectangular bottom for a roomier bag
• adding an additional strap
• adding some columns of stockinette stitch in the body of the bag to decrease the stretchiness
• making much wider straps at the base of the straps and gradually decreasing until the smallest part of the strap is at the very top