Whoa, those shoulder cape details...they're incredibly well shaded and coloured, I'm impressed! :D
The line art and colouring is cartoon and colourful, which I'm sure is exactly what you were going for.
There really isn't much for me to critic...
I'm not going to criticise the colouring samples on the side as I'm sure you left them there intentionally to show what went into the shading process.
There's no point in mentioning the background as this was a character centered artwork, but I'm going to anyway...it's a nice wall...:P
With that said, the only real thing I can say point out that could be further improved or looked at again would be Cirrus' left boot. It just looks like some of the colouring from the boot is going past the line art. This could however have been an intentional stylistic choice, in which case nothing needs to be changed on the boots.
Excellent work overall and good luck with your book. :P