Now that I've had a chance to look back, I have done a LOT of ghost related stuff. Since I actually love the idea of a ghost tfing people in various ways and not just taking over their body in a boring cliche kind of way, I guess it's natural. Heck, my favorite video game character is still to this day Gigi from Geist. But on to the list!
Actually one of the very first things I did for the process was a ghost tf, from the first ever Request and Sketch week even.
Sakura getting tfed into a catgirl by a cat spirit. :3
Pregnancy by possession?
Pregnancy by possession(s).
...and pregnancy by channeling pregnant spirit.
Gigi unknowingly randomly tfing people she flys past. Add to the face they don't actually SEE her and it's just plain fun.
Forcibly tfing someone to look more like the ghost via a possessive kiss.
...and a confused ghost girl that doesn't know she isn't wearing any clothes. 
Also, in my last run Lightning Round (number five) one of the contestants was the same ghost girl from the previous pic. She gets tfed in a few different ways, while still staying a ghost.
Contestants and rounds
1 2 3 4 and the
Prize pic.
I think that's a good amount for now. Hope this fits the bill.