...Nope. The result was ugly and incomplete. I was just checking to make sure it works.
How to fish: Open game in FCEUX, open Name Table Viewer. Placing the mouse over a sky tile shows the following:
Note the Tile ID: FA. Now open the PPU viewer:
The background tiles are on the right. Find tile FA. It is below the water, to the right of the question mark and two dots.
Now open up YY-CHR, Tile Layer Pro, or whatever your preferred tile editor may be. Find the same arrangement of tiles:
Note that the tiles are repeated, once for each frame of animation. Now you can either draw your own tiles or copy tiles from another ROM.
Now you know how to fish.