Hi Cheri. I really like where you're going with this piece. From the way the characters are interacting, it's clear that you have a good understanding of 3d space. There's a sense of depth to the characters that reads well for me. Your composition and use of negative space also seem balanced and pleasing.
I also really like the subtle colors and texture of the background. It feels like a foggy evening to me, creating a sense of closeness and calm. Is that what you were intending? For some reason, I really find myself identifying with the mouse peeking out from behind the lily pad. I feel my own curiosity piqued, find myself asking: What is the relationship between the mouse and the frog? What adventure are they about to undertake?
I think this piece could be even better if you spend some time looking at your line work. I do think line variation can add interest, so I'm not suggesting you make everything the same. However, this can be done in a purposeful way. For example, why does the outline of the mouse's tail suddenly become lighter and softer at toward the tip? I notice that the reeds and the curious mouse drawn in thin scribbly strokes, the lamp is drawn thick and almost wet-looking, etc.
Same goes for texture. The bumps/wards on the frog's skin contrast so much with the smooth surfaces of everywhere else, they really grabbed my eye. This might be a good thing if the wards are supposed to be the focal point. Was this your intention? If not, you might try painting them in a less-rough manner.
Hope that helps! I'm very much still learning all of this myself, so take it with a grain of salt.