Just a very quick edit with a few small ideas regarding texture. For the door, you can add texture to the outsides (top and bottom) and the middle can remain blank. To me, this gives a better finish than slapping texture all over a surface. It gives a sense of seeping damp to me as well.
For the mat, I've changed the single pixels (which contain no information) to double pixels, often married with opposite coloured counterparts. This should give more of an impression of actual texture (strands going in the same direction) and a little 3D from the contrasting colours.
I attempted to remove the box-like feel by getting rid of the hard borders and doing a little light-source work. (Imagine light coming from top-left as that matches the door.) Added a stain to the mat, softened the corners and gave it a bit of an angle.
Just ideas, feel free to ignore.
