yes, well i think that you have chosen a very hard background for your skill set. it has allot of noise and the light from the bricks - its a hard thing to do
but with that said what i would do (with the items you have shown here) i would change the hue on the cat- the background is very warm, then i would actually copy the wooden floor and combine it with the concrete in a way...because the current "concrete dose not match from my point of view it needs to be more horizontal - i cant explain in words but i would show you if u were here...
so
a. make a more intuitive background - work on the place between the concrete and the brick wall
b. remove the shadow that you currently have all around the cat
c. "blend the cat with the background"- you can even use the "burn option to achieve some results
d. the shadow of the lion should match the posture of the cat...
e. you are going in the right direction, make sure you use high quality JEPG for both background and cat
)
hope this helps