FB Chat Heads Enabler and Facebook Sticker Enabler. Both are free and easy to install. All you need is a jailbroken device and Facebook 6.0+.
I feel like the stickers feature is the least significant of the two, so we’ll talk about that one first. Facebook Sticker Enabler is a simple tweak that—you guessed it—enables stickers. It says it’s for iPad, but I was able to get it to work on my iPhone.
FB Chat Heads Enabler is similarly simple. Once installed it takes effect, so there’s no icons to worry about or options to configure. This one will enable the Chat Heads feature in your Facebook app (note that this is not the same as Adam Bell’s hack).
And just after you install the above jailbreak tweaks on your iPhone, go to Facebook app and try to chat with someone, you will notice a Chat Head appear at the top of the app, as well as an option to embed stickers. Again, keep in mind that these only work in the Facebook app.
Maybe if you have already got the two features from Facebook you can skip installing the tweaks on your device.