D7 Field template syntax
This is because you're rendering the full item when all you want is the url as a string, if you add this line of code in the template you will be able to see where the url is held in the $items array.

&lt;?php var_dump($items); ?&gt;


then you can find the part of the array where the url string is so your final markup would be something like this.

&lt;div style="border:10px solid pink;margin-bottom:20px"&gt;
&lt;a href="&lt;?php echo $items['url']; ?&gt;"&gt;&lt;img src="/download.jpg"&gt;&lt;/a&gt;
&lt;/div&gt;