Ah, just got it fixed, the issue was on my end. The front-page-12 was missing in the output.php file in the lib folder of your theme. I just went ahead and added/fixed it for you. Here’s is what it looked like before –
$opts = apply_filters( 'aspire_images', array( '1', '4', '5', '7', '9', '11' ) );
And here is what it looks like now –
$opts = apply_filters( 'aspire_images', array( '1', '4', '5', '7', '9', '11', '12' ) );
The background image is showing now so everything should be working.
Let me know if it works on your end.