Articulation Station: This is one of my oldest apps that is still one of my favourite go-to speech apps (although I now have quite a few more). It is quite expensive to buy the whole app, but you can purchase just the sounds you need individually.

For each sound there are 20 pictures in all word positions (initial, medial and final), with activities to practice single words (flash cards and a matching game), sentences (the kids love the rotating sentences), and stories.