Maybe you just feel like you need practice applying bias tape bindings. Maybe you have a presser foot that you just realized that you've never actually used for anything. A new project is a great time to learn something. Look for patterns that call for whatever technique or tool you want to try out, or think about how you can apply the technique or tool to one of your existing patterns. Think of interesting piecing.
Pieced fabrics can make for particularly interesting garments.
Perhaps you might like to have a stripe running down the front of your shirt from your right shoulder, or perhaps you want to go so far as to piece yardage from which to make your entire garment. Piecing doesn't have to be difficult. You don't have to develop a special pattern for a pieced garment - just piece the fabric before you cut the garment pieces. For example, for the above mentioned shirt with pieced stripe, you could simply piece a stripe into some yardage and cut the front out of that. Use fabric paint on black or white yardage.