how do i start layout after all image are drawn?

I have an issue after switching layout. At the beginning of it, an interlude starts with several things happening. I configure what happens in my XML file (walking, speaking, waiting events and so on)

I have an issue with my speak function taht is not triggered if it is called too soon (like for first) and i discovered that is for the "pick NPC sprite" in my function, because when is called the sprite is not yet drawn on screen. In fact if i put a wait 0,1 before calling function, everything works again.

WIch is the best way to start events in my layout after all is drawn on screen? (the layout is a simple screen with backgroun and objects)

Thanks!