I have oneproblem - newest 3d client dont have mull filesThere are two types of decoration. You can use one or both in conjunction, depending on the items.
1) Statics that are frozen to client files and distributed to players. (more efficient, but changes require redistribution again,)
2) Items or statics that exists on the server and are downloaded by players when they come in proximity to them. (less efficient, but more flexible when making changes)
All statics can be frozen, not all items can. Some can even be frozen but it is ill advised to do so, eg: doors.
CentrED+ (only the first method). Independent of Server. Directly writes to client mul files. You can also directly edit terrain/map with this tool.
Not sure if Pandoras Box still works on all newer clients, but Lokai has made this ingame SearchImage tool for finding statics. Once added you can save them to a server-side file with Nerun's static exporter for use with the [decorate command OR freeze them to map by using the [freeze and [freezemap commands ingame.