Many thanks to Rigel, GRNDL and madmike for sharing their symbols. One of these days I'll get around to mapping again, and I'll definitely make use of them!
edit: madmike, did you actually upload your dwg file somewhere? I went back through the thread, and I didn't see a link, but I might be suffering selective blindness.
Unfortunately, that set doesn't work for me. I want to be able to print the result on an 8 1/2 by 11 sheet, and Paint has a lower limit on how small things can get.
Sounds like you may wish to migrate to a more versatile image editor. Paint.NET, perhaps, or Gimp. Inkscape is also a pretty good choice for deckplans, but it's a vector editor, and so requires a somewhat different way of thinking. Not as different as CAD, but different nonetheless.
If you'd like some help and/or criticism, I recommend The Cartographers' Guild, which has lots of tutorials for the Gimp and Photoshop, and quite a few for other programs. Most of the traffic there is fantasy-oriented, but there are some modern and fantasy mappers, too.
Oh, and someone mentioned artifacts from saving as gif and jpeg. If you're interested, here's some technical information on those formats to explain it: Gif is an 8-bit paletted format that permits only 256 colors
total in an image. If you try to convert an image with more colors than that, then the software will do its best to simulate the missing colors by dithering. Sometimes it works, but usually it doesn't. Png is 98% functionally superior to gif and has thus superseded it. The only thing gif can do that png cannot is animation.
Jpeg does not handle line-drawing style imagery well. If you increase the compression ratio to about 95%, you'll eliminate most of the artifacts, but it will still probably distort fine lines slightly. Also, jpeg is a "lossy" compression format, meaning that it throws away information when saving. Each subsequent save operation discards more data, causing the artifacts to propagate. It is okay as a final display format, but definitely not useful as an intermediate or working format.