If you create several decals in one project, you can use them in another project.
To do this, click Manage tab
Settings panel
(Transfer Project Standards). In the Select Items to Copy dialog, select Decal Types.
Make sure that the image files for the decals are available to the target project. When Revit needs to access the image file, first it looks in the location specified for the file, using the absolute path. If it cannot find the file in that location, Revit then searches the paths specified on the Rendering tab of the Options dialog.
If you send the project file to another team member, you must also send the image files for the decals.