Normally, if you get turned into a ghost, there's no way to remain a ghost without losing your stuff. However, there's a glitch. Go to the arena, and have someone defeat you in combat. Then have an arena host boot you out of the arena. You will keep all of your possessions intact, and be able to move around Temuair (and possibly Medenia) as a ghost. You can't attack, can't be hurt, targeted by monsters, etc.
To be turned back, you'll have to return to the arena, and go into the arena combat zone, then ask a mundane to remove you from the arena. Then you will be placed in Mileth once more as an Aisling, and not as a Ghost.
Contributed By: Emhilradim.