Fantastic!! Awesome artwork. Love the character design, love the environment, very very good! And good choice in music!
I love all the layers you created - the foreground, the floating leaves, and the levels of parallax backgrounds! Very well thought out and very cool. I like how the perspective (camera point of view) shifts when you jump - cool! Great feel to the game. Keep going!!! Don't over think it, you may only need to add levels, instead of RPG aspects.
My only "suggestion", as a cat lover, would be to see the cats and hamster work together - maybe to fight some "evil force", like the Skeleton Army that killed the Hamster's (and cat's) owners and they are out for revenge or to rescue someone - with your art style I bet you could make something super cool. Just my 2 cents.
It's great though and you should do what you want! lol