I wanted to play with inlays of different woods, so I made a simple rectangular box out of cherry (all cut using a 1/4" end mill), and then made inlays using purpleheart and spalted maple (cut with a 90 degree v-bit).
I like the ying yang aspect of your project. I have made a lot of little boxes similar (ala John Clark) and used Watco Teak Oil to finish them. It looks like maybe your inside is unfinished. I bought from Craft Supply USA a lemon flavored wax to finish the inside of boxes. When you open t he box you get a gentle lemon smell and the inside is protected. I have used poly inside boxes before but every time you open you get that horrible chemical spell of polyurethane.