Update: Since Valve gave the Steam Community a fresh new look, Valve has disable artwork hub for games that's not suppose to have one. I believe the glitch still work I'll check it out later.

1. Go to this link with a desktop web bowser (Google Chrome recommend for this guide) - http://sp.zhabite.com/sharedfiles/edititem/440/3

2. Choose the artwork or GIF you want to upload

3. Right click on "Save artwork to Community Hub" & select "Inspect element"


4. Press Ctrl + F on the keyboard to bring up the search bar

5. Type in 440 into the search bar & then press enter

6. Click on the up arrows until you see a similar screen like the one below. The numbers near the arrows should say "13 of 14" (Subject to change)


7. Right click on highlighted "440" & select "Edit attribute"


8. Change 440 to the game's id you want to upload the artwork to & then press enter button - To upload artwork to Borderlands 2's Community Hub, you would want to change it to 49520


9. Close dat window & click on "Save artwork to Community Hub" to start uploading your artwork.

10. Please DO NOT abuse this exploit (eg. uploading unrelated GIFs or stolen artwork from Tumblr to the community hub) or else we can't have nice things on the net.
You can get banned by Steam support for doing this.