Most of the many related issues seem to be with paths, but externally linking and not using a stylesheet it still won't work. Using an image in the same folder as the code also doesn't work. The CSS validates on codebeautify.
.logo { background: url("http://findicons.com/files/icons/1620/crystal_project/128/keditbookmarks.png") left center no-repeat; background-size: 50% 50%; width: 100px; }
<div class="logo">some text</div>
<div>random stuff before <span class="logo">star</span><br>
empty span <span class="logo"> </span>after<BR>
<img src="http://findicons.com/files/icons/1620/crystal_project/128/keditbookmarks.png"/></div>
[jsfiddle](http://jsfiddle.net/Mousey/uhcpcy7k/)