Artworks - to sign or not to sign?

After my wife and I had completed a joint artwork (the photography was mine while she did the painting) and the piece was framed and hung on the wall, I was amused by the fact that we hadn't signed the piece! We discussed who should sign it - myself as the originator having taken the picture, in a sense composed it, or my wife who had painstakingly spent hours painting it? Paul Cartmell (eHow Contributor) states: "A signature on a piece of art generally authenticates an artwork as being created by a specific artist..." I thought that God doesn't sign his daily creations, every day is a masterpiece. He did that long ago: "God, Who made heaven and earth, the sea, and all that is in them..." (Psalm 146:5-6) through His word - a once off signature that established His authority as the Master Artist. So for now the artwork remains unsigned on the wall, my wife and I secure in the fact that we both created the work and had a jol doing so!