@ralphm @PaulOB I did some homework and the reason why the banner wasn't coming up as I was expecting on some devices was due to a missing ) in my code
Thanks for your help guys, your comments made me look deeper and what was going on.
<div class="item" style="background-image:url(docs/banner/Banner_059094020278.jpg">
<div class="item" style="background-image:url(docs/banner/Banner_059094020278.jpg)">
I detected this issue with an HTML checker and Google PageSpeed Insights seems to like it better, even on it the image wasn't coming up without that ). See for yourself