Your project image and headline are the most important branding elements of your project. It will be most of your backers' first impression of your project. So try to get an eye-grabbing, iconic image that can represent your project well whether it's small or large.

This is the image Pebble Technologies used to showcase their product, the Pebble Smartwatch.

As for a headline, try to make it attention grabbing and contain at least one keyword.