They look pretty good, but considering last month's security breach, I don't think hosting them on Imgur is a good idea.
Sure, when embedding from outside we would have been safe from that specific exploit, but what if they discover a different zero day and replace the image with their own exploited version? Just visiting /tech/ would infect us. And this is without considering they are already tracking us through third party requests.
I would recommend moving the background to /metatech/'s sticky, then linking them from here. 8chan allows internal links in the CSS whitelist.