You can decorate the food to spark his interest. Look up for bento ideas, the food are soooo cutely made up!
http://www.parenting.com/gallery/bento-lunch-boxes?page=3
Beautiful/cute accessories for serving food may also be helpful. Choose plate and cup that have characters your child like.
Another tips;
1) add sweet items in the meal. Example i put dried raisins/apricot/kiwi in fried veggies
2) modify favourite snacks. Eg add apple and spinach in pizza,or blend and add leafy veggies in DIY burger.
3) alternate milk with yogurt. So he won't feel forced to drink milk a lot.can also make your own popsicles using milk and fruits.
Hope some of these will help :)