If you want to make the image smaller in proportion (reducing its width but keeping the aspect ratio), you can use the content property with the url() function inside a ::before pseudo-element, but you'll need to use additional CSS rules to control the size. You can use the background-image property for this purpose, as it allows you to manipulate the size more easily. Here's how you can do it:
.yourcategory::before {
content: "";
background-image: url(images/icons/ico_lr.png?=v1);
background-size: 24px auto;
width: 24px;
height: 24px;
display: inline-block;
}