Are there any other requirements aside from being 64x64 for the alternative top screen image? I've tried to import one, but it doesn't show up on the preview.
I believe you need to import a 64x64 image for the top screen (primary). The editor will then change the top screen draw type to "solid color & texture". Afterwards it will show the top (alternative) icon pan down the screen if you have animated preview turned on.











