I have to admit that this is more useful than I initially thought.
Especially when you want to rearrange tiles.
The symbol function takes a little getting used to.
For example, it shouldn't be possible to drag the frame beyond the borders of the image.
It would be nice if the position of the frame matched the mouse.
Don't misunderstand - you can manage but it doesn't feel right.
The info where the icon or images are stored could be displayed longer.
Or alternatively be displayed as a tool tip when the mouse pointer is on the save button.
A "power of two" switch would also be a good idea that snaps the grid accordingly when dragged. (8x8,16x16,32x32,...)
Zooming in and out with the mouse wheel would also be useful.