Should I put a signature, watermark or copyright on my art before submitting it to the Wallpaper gallery?

It isn't "required" but we STRONGLY suggest it! As well, we recommend you put some form of identification on your work to mark it as your copyright. This can be done simply as text in a corner of the image, as a Ghost Image, as a Watermark across the image, or as a Digital Signature using software such as Digimarcs “MyPictureMark” which is available as a plug in for applications such as Photoshop. Doing this is the best way to prevent your work from being stolen. Some options to consider for protecting your work would be to include either: your name, your user name, or deviantART or other web address. Ghost Images and Watermarks can be virtually any image or text you desire, but you may want to be careful not to obscure too much of your art. Remember, this is meant to be displayed on a monitor!