Another PyroCMS field type. This one is called Image Select. Why? Because it does exactly that. It lets you select images. But wait! There is already an image field type. Yes, but that is for uploading images. Sometimes you just want to choose and image you already have. An image drop down is good for this.
I think a nice grid with thumbnail previews is even better!! I have the project hosted on github. It will also be submitted to the PyroCMS store.