How to add multi texture on runtime as "window" array

Hi,

I know I have to use EditorWindow, GUILayouter or something like that to accomplish it. However I'm really lost on it and I can't figure out which direction should I take to make it happpens.

I want to add a button to create on inspector window a "zone/rect" that user can add a texture, so, if I hit the button twice it will create two zones for two textures as well.

Something like this Picture shows:

I've made so far this screen:

This is not exactly what I want to. However this is the beginning to accomplis what I want to.

Thanks and sorry about my english.