Displaying the album art is pretty simple.
Volumio exposes it through the websocket already, just need to add it.
Just add/change the following the MMM-Volumio.js file
item.className = 'mmm-volumio-item';
item.innerHTML = '<div>' + data['title'] + '<div>'
+ '<div>' + data['artist'] + '</div>'
//+ '<div>' + data['title'] + '</div>'
+ '<div><img style="width:25%;height:25%;" src=' + data['albumart'] + '></div>';
it seems the site is removing the formatting from the code
Here is a screen shot of the changes.
I would say play with the layout as it suits you. I had no need for the album title (the reason the one line is commented out).
My version is one the bottom bar.
You will most likely need to play around with the css to match your layout.
One other note if when you first load the module, if you don’t see anything playing (assuming it’s playing on Volumio), stop then start the song again. After that everything will change automatically.