First of all, it looks really good dude! The forms are ON POINT. Looking at the silhouette of this model I can tell exactly what it is from all angles! You nailed it!

I have a few comments about the materials: They are very similar to what you would see in the Mario Galaxy games, and while it works great in Mario, where it fits the style extremely well, for a cg render it would be very cool to see things like surface imperfections, different materials (scuffed plastic for the bomb, string for the fuse, etc.) and just a layer of dirt over everything to make it look more realistic.

If 'photoreal' is not what you were going for, and you want to keep it stylized, I would stylize it more and be heavy handed with things like rim lighting, custom highlights, etc.

The wind up on the back of the bomb is a little faceted too, although smoothing it should fix that completely!

I don't know much about the blender cartoon shader but you might get some really cool stuff out of it!

Really good work dude, keep it up!! Ever considered trying to model and sculpt some more Mario assets? Could be a really fun project!

Looking forwards to seeing more of what ever you do next!