on start of layout
repeat x times ----> system|create *x_object* on layer *Y* at ( random(LayoutWidth), random(LayoutHeight) )
Oh sorry, this isn't what you want. You want to create and distribute the objects randomly from within the editor, not at run time. There isn't a way that I know of...
Closest thing for variation purposes is to do what Hardty said.
on start of layout ----> x_object | set position to ( random(LayoutWidth), random(LayoutHeight) )