I have your mod downloaded, so I thought I'd post a comment. Even if its 6 years old Cx
The old shells in tf2 were static and didn't move around much, maybe spin a bit. They were also flat and visually displeasing, at least to me.
This mod adds some depth by making these 2d sprites seem 3d through a simple looping animation, not to mention that the shells themselves also look really nice even in screenshots.
There are some cons, but not really any that are fixable to my knowledge. First of all all the sprites are at the same point in the looping animation at any given time. Second of all, once they hit the ground, they continue to spin which makes them look odd when they stop moving on the ground.
all in all, a great mod, 9/10, not that I can rate it anymore x3
Pros: It's something that I feel that everyone should need to download, whether you play Heavy or not. It's just basically better than the default.
Improvements: I don't think it needs to be improved.
Notes: Why didn't Valve think of this?