Neat piece! I can totally see the toad playing his violin there. There are a few points of criticism that I have:
The piano sounds pretty artificial, not so much in the timing, but in the velocity of the notes; it sounds like every note is hit with the exact same amount of power.
Other people have already mentioned this, but until 2:05, there isn't enough variation in the piece to warrant it being as long as it is.
Speaking of the finale, I think the instruments could have fitted together a bit better. The piano and the violin don't change (much) to accommodate the inclusion of the gritty bass and the beat. Some reverb to give the section some more space and grandeur would've served nicely to capitalize off of the tension. I also think something like a choir would've fit nicely here, though that may simply be personal preference.
Not a real big fan of how you handled the kick snare pattern. It's nice to different things, but this feels like it's being different for the sake of being different; it comes across as a bit chaotic, and, in my experience, makes the rhythm a bit more difficult to listen to.
My last piece of criticism is that the silence right after the drums cut out and the piano resumes, at 2:56, could have stood to be a bit longer, actually. That would've nicely drawn out some lasting tension, and given the closing piano a bit more depth and impact.
All in all, I think it's a nice rendition of the image as music, and I can see where the inspiration came from. It could use some work, but that doesn't mean it isn't a good piece. Well done!