Layout images in form of a number
<p>I have a folder with small images (Facebook profile pictures). I want to make a new mosaic-like picture where all the small pictures are laid out in the form of a number, like in this example (<a href="https://theamt.com/800_member_milestone_reached.htm" rel="nofollow noreferrer">source</a>).</p>

<p><a href="https://i.stack.imgur.com/VGAFF.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VGAFF.jpg" alt="enter image description here"></a></p>

<p>Is there a software program that can do this (and that runs on Windows 7)? 
Otherwise I'm also open to writing a small script to do the same. 
I know how I can add a white border to the images with PIL/Pillow, but my searches for how to layout the images have turned up fruitless.</p>

<p>Can anyone point me in the right direction?</p>