Is there any tutorial here on Otland about ObjectBuilder?try with this custom ob, u will also need to add the item in itm editor to modify itm.otb the add items.otn into yours servers items folder and mapeditor
Hmm, can't really understand what you mean with mouseover the imagesfirst find the item in the left panel , then edit or just double click it , then just mouseover the images and it gonna give u the sprite id of each image
Screenshot (http://prntscr.com/mcy2rq)