Some of the new wall decor is already in the game. The art labeled trophy art for each of the PVP matches is set to pick up. If you haven’t done much PVP over the years you may not have the required achievement. If you have then you will need to pick it up the same way you claim the class signs.
The achievement you need is the last one in the “Kills” section of each PVP match type, all the way at the bottom of the list. If you select the last of those achievements you will see an icon for the art piece. Right click that icon to have one added to your available décor. You can have 50 of each one should you be inclined to click that much.