Someone has done it before and I have inherited it. I would like to know how to replace the default drab looking icon of a web part list. As shown in the screenshot some icons are already there but I don’t know how to do it and I have to do it for the ‘Forms’ icon.
I solved this myself by going into the ribbon and changing the view of the web part that has the tiles to ‘All Promoted Links’. Once I was on this view I could easily edited the ‘Items’ which then opened a new page for me to edit each Tile individually. This interface allowed me to specify an image from the ‘Assets’ folder. Only thing to note is that the images had to be in .png format.