This is what I've been working on in the home for the past two weekends. Finishing up a half-assed attempt at Faux Venetian Plaster by the owners of the house we are renting. They had put up one coat and then attempted to burnish it with a big putty knife. Um,...no. You put up two coats then sand with 400 grit,...then 600 Grit and polish with a dry cloth.
They had also not bothered to remove any of the switch plates before plastering. Seriously how hard is that? Some switch plates were covered in plaster while others were there was a white border where no plaster had been applied.
This was the room as it stood on the day we started moving in (September 17th)

Attempt at an Egyption motif,...but the alternating blue and gold squares were not connected on the archway curves.

Just to show off some of the half-assery; this was the first day of working on the project. It doesn't appear as though any attempt was made to mask off the ceiling (south wall).

They just plastered directly over the wall paper on the east wall.

Their idea of burnishing (the homeowner's wife IE the brains of the operation is supposed to be an artist).

The above photo represents the best looking portion of all the walls (this is the north wall) or at least,...something of what it's supposed to look like,...the remainder of the wall (let alone any of the other walls) there was no burnishing attempted.
This is the north facing wall as it sits today.

I put the second coat of plaster up and polished it. I also put two coats of plaster around the doorways and to me it gives it a cleaner look. I do like the alternating squares on the under sides of the archways so I left them.
I took off all the switch plates and had my wife clean them up will I applied plaster around the exposed holes for the switches.
Got started on polishing the west walls and still need to put second coat on and polish the south wall.
The east wall (the one with wallpaper underneath) I'm inclined to leave be.
Then I will have to figure out what I want to do for all the white woodwork as it could use a fresh coat of paint.
BTW; If you are thinking about DIYing venetian plaster walls,...do yourself a favor and don't. While it's very rewarding and I love the finished results,...it's a lot of hard work. Just pay a contractor to do it.