Line a sieve with cheesecloth or paper towels and suspend it over a bowl. Pour the yogurt into the sieve and allow it to drain, refrigerated, for 3 hours or overnight.
Place the thickened yogurt into a medium bowl and stir in the raisins, walnuts, vanilla, honey, and orange zest. Thin with orange juice until it is a desirable consistency. Garnish with sections of orange, orange zest, raisins, or walnuts and serve.