you cant modify this.  as far as ship pictures go, its generaly by either roll, or the order in which they are listed in the Player(race).entity file. other icons are generaly speaking , not movable. unless you mean like ship icons which would be located in the Texture (for the actual graphics) and window (for the locations on each icon pallet).

well, 3 things to look at, texture folder for all the base files, window which holds all the references for the icons. and then the actual ship/structure building which links to the window files.