That's what you say now.

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 program itself doesn't care about them, but Windows likes to have them available for uninstall/modify/repair action called from the control panel/settings. You might get errors uninstalling if they are not present.

Dragging and dropping an image into CC3+ is the equivalent of doing a Draw -> insert image, but it skips the dialog box. Unfortunately, this also means it skips the dialog where you can turn off the border, and uses the default which is applying a border to inserted images.

You can turn this off by using :CC2EDIT: on the images, and turn on the hide outline option. Unfortunately, this can only be used on one image at a time (Don't worry about the purple selection rectangle this operation seems to leave behind, that goes away the next time you select something else)

The better way to insert symbols to avoid this in the first place is to do as Raiko suggested, and use the :ICON_CATALOG: button and browse for your folder. This will show all the images in that folder in the symbol catalog window, and you can insert them the same way as regular symbols.

If this is symbols you are going to use often, the even better option is to make proper CC3+ symbol catalogs for them. This allows you to set up scaling and things correctly in the symbols themselves, so you don't have to re-scale every image inserted, among other things.

Stunning as usual. What monsters hide in there since an initiative roll was called for? Some dryads wishing to take revenge on whomever stole those canopies?