Didn't have time to do too much, but I started to work on one of the final features needed to make the editor complete. Most normal editors use drag and drop as a means to transfer between depths. However, in my case not all the depths are visible at the same time, since the new 48x48 size takes up too much space and displaying all the sizes would be prohibitive. That's why I have a popup menu. So for the transferring among depths I decided to make it so that the user could hold down option (the standard copy modifier) when selecting a size from the the menu and then the contents of the current depth would be transferred (and dithered down if necessary) to the newly selected depth.
I decided that to make it very obvious that holding down the option would trasnfer the depths I should change the cursor to the standard copy cursor (the arrow with a little plus sign). This cursor is stored in the system folder with an ID of -20486. So I added the cursor setting to my HandleContentClick if option was held down and the user had clicked on the popup menu.