This is just a simple Chrome extension I made that hides the Facebook ad column on the right side of the game page. It also allow you to load a custom background for the game page. Once installed you'll see a little orange BG (background changer) near the server selection widget at the bottom of the game page. Click on the BG to expose the background changer. The extension will remember the change the next time you come back to the game. There is even a check box to decide if you want to use the original size of your image or stretch it to fit the window. Images need to be hosted somewhere on the internet. You'll need to paste in the images URL. For example, the URL of this forum's background is:
I've attached a screenshot as an example of the game with a custom background.
It's free so check it out and have fun!
Looks like they are taking down my links to the extension so just search for Super Hero Sidekick on Facebook or in the Chrome store.