Wow, that's really weird. I notice, though, that the top of the pit, and the bottom of the wall, don't have this problem, so I'm going to mess around in Photoshop for a bit and see if I can come up with anything. ...and I'll come up with something for the crumbly walls while I'm at it
I just realized that that's just how the game renders the tiles, and there's nothing we can do about it. I did notice that the tiles were slightly off, some of them were one pixel too low, and I corrected that in my tileset. I also noticed that the colours for the pits are so close to those for the ground that it's very difficult to tell the difference at first glance, so I might suggest changing them a little.
As for the lines around the walls, I'd actually suggest changing what makes up the walls rather than darkening the floor tiles, unless you're planning to make it a cloudy grey sky, in which case I can change the colour of the spiders easily enough to nearly match whatever colour you make the clouds.
Edit: Attached is my edit of your style7tiles.bmp file, and I tossed in what I envision for dropping trapdoors in the tile as well as crumbly walls. I also raised a few of the tiles to where they should be, and redid pits to make them much closer to the dark, ominous clouds I think you were going for. I also tweaked the walls to make them line up a little better.
[Edited by DiMono on 08-06-2004 at 03:06 PM GMT]
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Deploy the... I think it's a yellow button... it's usually flashing... it makes the engines go... WHOOSH!