Underline headings with images

What I’m trying to do

I want to create an underline, but one with an image in the beginning and on the end. See the example:

This is my current H1 style:

h1, .markdown-rendered h1, .HyperMD-header-1{
	text-transform: uppercase;
	border-bottom: 3px solid #CFAD8D;
	width: 100%;
	display: block; 
	text-shadow:
	-1.5px -1.5px 0 #d2d2c8,
	0   -1.5px 0 #d2d2c8,
	1.5px -1.5px 0 #d2d2c8,
	1.5px  0   0 #d2d2c8,
	1.5px  1.5px 0 #d2d2c8,
	0    1.5px 0 #d2d2c8,
	-1.5px  1.5px 0 #d2d2c8,
	-1.5px  0   0 #d2d2c8;	
}

Things I have tried

I’ve tried the border-image css property and the background-image properties but they don’t seem to work. The two images (border-left.png and border-right.png) are in the sale folder as the css for the theme I’m using. For example:

	border-bottom: 3px solid #CFAD8D;
  	padding: 15px;
 	border-image: url(border-left.png) 30 round;

But the image doesn’t show up.

How can I achieve the example as seen in the image?