It isn't something developers have a need to do very often, but you can set multiple background images on a single element.

Example:

.element {
    background: url('image_path') center repeat, linear-gradient(transparent 0%, #000 100%) no-repeat;
}

What can you do with this? It's only limited by your imagination, but I'm personally a fan of always using as few elements as possible when working on a project.