Can I Play...?

All right, so this is finally some insight into Kaoru's past, I've been trying to figure out a backstory and now I've got something of an idea of what it is.

She's gonna be an alien part of a race of froglike beings like her, all are based off of poison dart frogs found in the rainforest,
for instance, the yellow girl is referenced from this: [link] The golden poison dart frog, ironically one of the most poisonous of the species,
the green and black one being a boy: [link] A green and black poison dart frog, I think I need to work on him some more, the pattern didn't come out like I wanted it to,
and the reddish one: [link] I love LOVE the colouring on this one, and I like how she turned out,

Basically the three are playing and Kaoru wants to play too but she's too shy to say anything so they're just playing tag without her, like kids do. The clothing they wear is very light and flowing because they live in a hot rainy climate, I tried to show that in the background that they were in a rainforest.
I did not draw that background, I used this picture: [link] and used this cartoon photo tutorial found here: [link] by: ~SilentWolf1

So I need constructive criticism on this, tell me how I can improve, ^^