Paint-over

Lin Lin Bao, Try something like this.

Just a quick 10 minute paint-over.  The seats look a bit too shiny in mine, but there are a few things I'll point out.  Remember your light source.  It'll be valuable in everything you do.  Local color is important.  One thing to notice is the way that the wall should be constant in color all the way down and maybe gaining a bit of saturation while also gaining value.  Notice how the shadow under the seat allows for a distinction between floor and wall.  The windows should reflect the environment to an extent.  Think about what's on the opposite wall just a little further down and drawing it over the window--it works fairly well.  You ceiling (if it's behind the light source--depends on what type of lights there are) should still feel normal with a relatively strong light on them.  I hope this sort of made sense  ;-)  You're a great artist, and you'll continue to rise above yourself and get better everyday.  Cheers!