How do I get a div to automatically adjust to the size of the background I set for it without setting a specific height (or min-height) for it?
Another, perhaps inefficient, solution would be to include the image under an img element set to visibility: hidden;. Then make the background-image of the surrounding div the same as the image.
This will set the surrounding div to the size of the image in the img element but display it as a background.
<div style="background-image: url(http://your-image.jpg);">
<img src="http://your-image.jpg" style="visibility: hidden;" />
</div>