In order to actually be able to this, you will have to spend a little bit of money.

I've seen people recommending different "corrupted" backgrounds but they are usually a few dollars. The cheapest one that I found over the time is the one I'm using and it's a profile background from the game "The Land of Dasthir".

You can find it here

As of this guide is created the steam background is worth ~0,15€

Now that you own the background you can go to your profile and choose either "Items Up For Trade" or "Item Showcase". This profile background needs to be wherever you want it to be blank. Which most likely should be the first two or so.

The background will look like one of these in your inventory.