things to consider when intergrating a picture:
colour / b/w (even if the destination picture is in grayscale like yours, you can make it either colour or b/w depending on if you want to match it or to make it stand out respectively)
saturation levels: big buck right about this- a way to stop it looking so pale and washed out is to increase the saturation, which was i think about the only thing wrong with yours.
colour: the colours fine in yours but you should always check it just incase
lighting: in my experience 9/10 times the lighting is the only thing wrong when intergrating a picture. when it comes to lighting in pictures there are two types:
when there is an obvious light source which isn't obstructed (like strong sunlight outdoors)
these types have:
hard shadows/highlights
soft shadows/highlights
when there isn't an obvious light source, and more just general lighting (common in indoor scenes) like yours is
these types have
soft shadows/highlights
sometimes no definable shadows/highlights
just think about these things you'll make a lot more realistic pictures.
try adding some atmosphere aswell
i do that by adding a soft black around the outside not too much, just adjust it untill it looks right.
this kind of thing
perhaps this is a little much
i hope this helps you