Looking good ! The only thing extra that I would like to see is some vibrant coloring.
I went by our local art foundation and picked their brain on acrylics. Before I left they let me take home several tubes of various colors to experiment with.
Just use your scrap ivory to experiment with ,varying the amount of moisture that you add to the acrylic to achieve the desired effect. Tagua nuts make excellent pallettes to practice on.
Of course, we have an advantage here in Texas as we are required to color our schoolwork through the 12th grade!!!