and oh, you cannot edit the vertical flipping on the terrain editor (only the horizontal rotation can be edited on the terrain editor)... so for each vertical angle that you need, you need to create a new doodad...
the facing angle (fixed rotation) is on the upper portion of the object data... anyway, its just if you need to do horizontal rotations... (oh I typed it wrong, fixed angle should be set to -1... ^_^)
here's a test map with rotated thrones... another note, it looks awkward with the roll angle set to -90, try setting the roll angle to 0.00, it looks better...
(NOTE: you will not notice the rotation before you actually place it on the map, the doodad placer will still look like the default throne...)