Your rules are fine, it just need some categories for future needs and website upload. Logo contest (atleast much higher reward) is a separate one from other lizi images which should be unique and for LIZI only. I prepare you images as example, I choose category of Sports and Food, hope you like it.
These reminds me of Today image coin, lol.
Food image 1-Lizi restaurant
Food image 2-Lizi Coffee shop
Sports Image 1-Lizi tennis team
Sports image 2-Lizi Basketball Team
very good .every image reward 30lizi had send,if it is the winner i will reward 100lizi after a week.