Hello
Today I will show you how to make a bas-relief from plaster on a wall.
I would add that I really have nothing to do with artists or painters.
I am an ordinary accountant who seems to be doing some people
I'll try it too.
After renovation, ordinary plaster for finishing coat was left, I made a outline of a tree with a pencil.

And to work!
In the bowl I mixed up some rather thick plaster and thin layers
(if it is too thick, it will crack after drying)
  I applied knives, teaspoons etc. to the wall with various kitchen utensils.
and smoothed with a brush dipped in water.
After drying, I primed, bought colorful wall paint samplers
and I painted it.
I made this tree 4 years ago and nothing happens. Does not crack, does not crumble.
Good luck, it's really not difficult.