At the very least, a bag is a blank canvas waiting to capture the sum of your fencing experiences--where you have been, what you have done, what weapon you espouse.
My bag is easy to spot, natch
If you don't like the bumper sticker aesthetic, you can always go with an Etsy vibe
The crafty approach works pretty well for the weapon bag,
Or cute little bags for your body cords.
Not into crafting? Focus on practicality. Your bag can be ferociously well organized, as demonstrated by Mr. Ridley here:
Wow, this is like the California Closets of fencing bags.
Remember, your fencing bag is your traveling companion, your lifeline, your warehouse, armory, pantry, first aid station. Give it some attention, a little respect, lavish it with a modicum of creativity, and it will pay you back ten fold.
And if all else fails, it makes a pretty good pillow, too.