All of it looks out of place...
The render that you have used seems like a good choice with the BG however, putting it in that bubble seems pointless because you've removed it from a scene where it fits. ATM the render looks like it's in the sea. The cat kinda just looks put in there to fill space. The random fractle in the corner isn't doing anything and the BG + Cat looked overly topaz'd or cartooned. Also, you have no need to put a watermark on your work.
IMO you should work on getting just one or two elements perfect then build up from there.
I love the Quality of the Manip. However, I do agree with what was said above; The cat doesn't really look like it should be there. I also think the bubble could use a little more work as far as blending and tonal perfection