The only problem I've found most annoying on using background-image on the CSS files is that you're bloating the CSS for nothing. You can inline that background

The only problem I've found most annoying on using background-image on the CSS files is that you're bloating the CSS for nothing. You can inline that background file and remove a lot of KBs (assuming you use lots of backgrounds). The SEO part to me became irrelevant long time ago since all the traffic is driven by ad campaigns.