Cards are typically used to promote and link to content, and are not usually a stand alone design component.
Standard Cards with Squared Image
These standard cards typically have a concrete background, but can be inverted to be white if they are used in a non-white band.
No-Image Cards - White with Border
No-Image Cards - Light Gray
Standard Card Variations
Cards have an option to use round images (images will be displayed at 160px wide and tall).