I don't think your humor is defective, it's just a tough concept to pull off in the way you've chosen. The MLB, NBA, and other variation logos have pretty well defined and recognizable silhouettes.

I did this one with an image I created for another project. It's probably too serious, but you can tell it's a pack.



Since the other one was too serious I threw this one together quickly:



There's a bunch of different ways to go with the idea you're working on, but I think the key is going to be defining the bag so that it's easily recognizable. You could probably just as easily make the image a duffel bag.