Okay, starting with a quick tweak - I desaturate the background layer using an adjustment layer. I also add an overlay layer that's masked to just hit the walls.
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First create a group (folder icon) and mask the folder so that the floor is masked out and the walls are open. In the group create a new layer.

Now select the path that surrounds the floor. You don't want to have a selection going round the outside of the walls, because we're going to stroke the path and we don't want the outside of the canvas to be highlighted.

With the path selected go back to the layers palette and have the new layer selected. Pick a nice large brush and press enter. You'll see a big fat line stroke the path! Ctrl-z to undo. You should now see what we're doing here.

This should be something like what you just produced:
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So get rid of that big fat line and we'll do something more subtle. First off, I want to put in a grungy highlight along the edge. I use a large grungy brush with a low opacity (around 10%) Start off really big - like 100-200px - and stroke the path with white (hit enter). Then reduce the brush size and do it again. Rinse and repeat until you have a nice gradual highlight up to the wall edge. I set the layer to overlay to get a nice textured highlight:
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