I like what you tried to attempt with the fire-based creature alongside the water-based creature, and I know that the design of the water-based creature isn't your own so I won't comment on that.
Composition-wise the piece is well put together if not perhaps a tad lacking in details. A few variations of form on the grassy area and the water would go a long way to adding some extra personality to the piece (such as dips and break-offs along the shoreline, rocks, leaves, visible tree roots, etc).
Related to that, the lack of planned detail on the background is a little evident. The characters look as though they were sketched out will intent and the background was added as an afterthought, which somewhat ruins the impact of the piece itself. The pre-made appearance of the grass and the water also takes away from its impact. This can be avoided by adding underwater details (since the water looks as though it's meant to be crystal clear and clean) such as the bottom of the pond, floating debris, etc and drawing individual patches of grass, dirt, rocks, etc yourself.
In terms of lighting the piece looks very bright and chipper, which is a plus, but the manner in which you've chosen to apply light and show is very underdeveloped. It kind of looks like you used something similar to the burn/dodge tool in photoshop (I won't pretend to know for sure) and it definitely doesn't work here. What you might want to try is manipulating the base colours of objects and characters in order to get your shadows and lights. For example, for a base blue colour (like on the Ficatt) you can mix darker blues with purples to create shadows, and lighter blues with greens to create highlights.
(You can check out a colour wheel to see what colours you can use for traditional shadows and highlights. Typically you want to use the colours on either side of your base colour for shadows and highlights but you don't always have to use the same ones for the same thing. You can also use intricate colour combinations to convey very specific feelings or atmospheres--like using blue as a base, purple for shadows and pink for highlights to create a cool and calm feel with a stark contrast and light source.)
Overall I like what you tried to do with this piece, but it will benefit greatly from more attention to details and a better usage of the bright colours on display.
That's all the critique I can offer up at the moment.
Hope that was helpful~