Thank you all!
Richard and Dianne : I'll try to take few pictures showing the panel and some details as soon as I have time.
Dianne, there is not really one recipe to paint a trompe-l'oeil : some people will paint on regular canvas... It's the result which is important. You know that a trompe-l'oeil is well done when people don't notice it when they enter in the room, they just think it's real objects. For this, I love to paint on cut-out panel, it allows more liberty on the choice of the objects, and I always varnish with a mat varnish ( If you see the reflection of a glossy varnish, you know immediately that it's not a 3D object. )
Of course, including some figures in a trompe-l'oeil is not supposed to be the best idea, because only inanimate objects will really fool you. But it's my new way of doing things, a mix of a figure painting with some trompe-l'oeil parts.
my first attempt worked well : the first day it was hang in the window of a gallery, someone ran in the gallery saying " Help! Your frame is falling! ". This is the best compliment someone could ever tell me !