Whenever I have "nothing to photograph", I fall back on composition. Line, shape and form. All images come down to this, in the end.
There are obvious questions when photographing other people's artworks (being it sculptures or graffiti), but in the above case, my motivation was pure - practice practice practice. I strongly feel that without constant pushing of the boundaries, and continual question of creative assumptions, there is no way to grow as an artist.
I have always loved "ghost" stickers, and this one, on an aluminum pole, was particularly striking to my eyes.