Don't be afraid to go with light lights and darker darks. Doing this is going to not only add more depth but it will also give you more variation of value so you can more accurately represent your forms. Next up focus on working on developing your focal point. As it stands right now you have two hands gesturing towards one another where their is an anticipation for the two connect. This anticipation really makes this area the focal point but the index finger of the left hand lacks value variations as well as detail making it less of a focal point than it should be. Edges play a huge roll in focal point with hard edges being more of a focal point and soft being less. The finger has hard edges and that helps it become more of a focal point, and it's darker value contrasting against the white also helps it. In the future emphasize focal points by keeping in mind your edges (hard and soft), details, lighting, and value of the subject in focus. Over all great work!