These are the graphical defects I can think of that I intend to fix:
- Inconsistent coloring in some of the snow tiles (a few of them are more
white than the rest)
- Seams when tiling the castle tiles
- Lack of a proper freeze sprite for the flying Spiky
- Lack of a "break" effect when crates are broken
- Lack of a "shatter" effect when an ice bullet hits something
- Ugly rusty spring compression images
If you're asking how many images are in a tileset, it depends on the tileset.
The castle tileset has 30 32x32 images in total, while the snow tileset has
around 200 images of that size. I think the cost of replacing one would
generally be about the same as the cost for replacing an animation.