Help with Custom Field Custom Dropdown

I am putting the finishing touches on a theme for a client but I am stuck on a particular need.

This is a movie critic’s website and needs the ability to select ‘star’ images when the post is created/edited and have them show up in a particular spot on the posting. Basically, there would be a total of 9 selectable ‘star’ images (from 0 stars, including half stars, all the way up to a possible 4 stars max).

I was thinking it would need to be a custom field on the post page, but I am at a loss as to how to properly tie it into the post template. The images would be with the rest of the theme images.

If anyone could point me in the right direction or give me some guidance to help me understand the relations, I would be most grateful.

[No bumping, thank you.]