Remember when Twitter was just a 140-character microblogging platform?

The service today added in-line images and videos to timelines accessed via and Twitter's mobile apps. Depending on how many accounts you follow, this new ability to view image previews without clicking or tapping a link could save you some time and make your feed more visually interesting — or make it maddeningly longer to scroll through.

Curiously, the image previews can be turned off on mobile devices (they're turned on by default), but not on the Twitter site. We’ll have to see how the change — which affects only images uploaded directly to Twitter or videos posted to Twitter-owned Vine — impacts engagement with tweets.

A recent study showed images were 94 percent more likely to be retweeted than other images were, a homefield advantage that could grow larger because poor Instagram and Facebook are left out of Twitter's image preview game. There's also evidence that Facebook's introduction of larger images in page posts this summer significantly impacted engagement.

Also, of course, sponsored tweets just got a heck of a lot more appealing — for advertisers, at least.

Meanwhile, Tweetdeck already offered the option to preview images in three different sizes. And, crucially, it also offers the option to turn image previews off — for now.