making my own items

i was playing one map n i saw that mapcreator make his own items...like normal maul to hammer(human upgrades>grifon hammer) or took a golem n its look like plate armour... know how he did this?....thanx

You can do this using one of the enhanced editors. All you need to do is edit/create a custom item and change the interface icon field to the path of the picture you want from the MPQ. Most of the enhanced editors also come with a useful text file which contains a list of icons and their paths.