I would check over at orbsydia for more on setting up your custom graphics. There are many people over there that are very knowledgeable on this topic
http://www.orbsydia.ca/Once you have patched them into your .muls, and have configured any of the files required to reference them, then you would access them just like any other graphic by referring to the itemid, gumpid, bodyvalue, etc. that would depend on how they got patched into your muls.