iOS Custom Keyboard with Images instead of letters

I have to implement a custom Keyboard with Images instead of letters, exactly like that one Ikea Emoticons App

I've tried some tutorials and examples but everything I've found is for making custom keyboards without Images (just with letters).

I just need to show some Images, and send the selected one as an Image.

Any ideas about how is it implemented in the IKEA app for example?

Here is what I have tried:

AppCoda custom Keyboard

WUEmoticonsKeyboard