I've found very cool and simple way to deal with a preloading. Since all the approaches for preloading images are not satisfying:
1. wix suggests to hide preloading image in page onready event, but its only starts to shown after all elements are ready
2. custom html in header area only shows when site is loading and disapears too soon
So , i set all pages background image to preloading! and it is showing before all elements, as it is a master background , all i need to do is to hide it in each page onready event.
But there is no background property in page element... Any ideas?