For your first iteration, I love the illustration but I think the box on top of the image takes away from the illustration itself so maybe think of sollutions that could avoid using the box. As for the overall typeface, I think you should experiment with choosing something a little more playful or expressing that is not so narrow.

For the second one, I love the illustration and background color, but I think you need to work on/watch out for your margins. They get a little tight on the mobile one.

For the last one, I think your stroke width around the speech bubble is a little too thick. Also I think you could do something with your background to make it a little more interesting/add depth.

Overall great job though!