Which ones you have installed can be checked via Tools -> Add Ons. (Only shows those that have been installed with the full year installer, so won't be listed if you have installed each issue individually).

That means it is an old map from before CC3+ (Or it was created from a flawed template that wasn't properly updated)

The default data file location was moved between CC3 and CC3+, and the # symbol refers to the installation directory, where the data files used to be kept. CC3+ has a fallback that it will be able to still display these files, but I guess the symbol import doesn't check this.

Fortunately, it is easy to fix, just run the FFIX command in your map to automatically convert the paths.

The button can easily do that already, all you need to do is to change the master filter to an asterisk.

Just right click :CC2SYMPATH: and pick master filter settings. Set the active filter to an asterisk (*). Now when you click the button, it will show all the structure symbol catalogs.

Note that you can save the modified master filter if you wish, but I strongly recommend NOT saving it over the existing ones. There isn't a reset to default button, so you can't get them back without reinstalling or manually changing them back.

If you save as your own filter, you can load this automatically from the map load macro (OnOpenMacro map note) if you wish to have this behavior always with your map.

Note that this gives you easy access to all the individual symbol catalogs for structures. If you want all the symbols in the symbol catalog at once, you need to do as Raiko says, make one big monster catalog containing everything.

To get started with lights in your map

1. On the SYMBOLS sheet, deactivate the Wall Shadow, Directional effect, and set up a new Wall Shadow, Point Light Setup effect, with a shadow length of 2
2. On the WALLS sheet, deactivate the Wall Shadow, Directional effect, and set up a new Wall Shadow, Point Light Setup effect, with a shadow length of 0
3. For this particular map, there are no other sheets that should cast shadows after this, so also add a Wall Shadow, Point Light Finalize on the WALLS sheet.
4. Right click :CC2RESMODE: and pick Global Sun. Set the transparency of the shadows to either 0 or 10% to get nice dark shadows.

You may want to edit that light of yours to have a bigger radius if you desire more illumination. Use :CC2EDIT: on it to do that.

DON'T do that. It's going to cause you all sorts of headaches in the future. Since the path to the images are embedded in the map, it means that the map file won't work for anyone else not having the images copied to the right place, including on your own other/new computers. Leave official artwork in the folders they were installed in, and import them from there. Only make your own copies if you are going to actually modify the .png files on disk themselves, in which case you obviously need a personal copy.