Part of the problem may be caused by the fact that it looks as if your carpet going up the stairs slices away the lower part of the ceiling tile - i.e. the upright bit.
Next, I'm not sure if you are using the corner shadows from the big rectangle, because it looks as if the shadow going up is darker than the shadow going across.
Finally, set your shadows to star passability if you are using them from a B-E tile sheet or 'Above Characters' if they are events, and then they will fall on the sprites, instead of the sprites standing on them.
Slightly different issue, but you will help your perspective if you also shift-clicked the final, top tile of carpet in the vertical corridor so that the pattern ends with the shadow. That will increase the impression that the carpet is running behind the wall.