I think if I were a bird, I'd be a magpie. I like to collect pictures of shiny objects and put them on collages. This week's theme is about gold, silver, copper, aluminum, stainless steel, and so on: shiny metal objects with reflections. (And let's not forget chrome, on old cars!) The reason I like them for collage art is that they're a way of bringing light into a collage—although shadows are another way, of course.
Caution: gold and silver pens, mylar, foil, and other reflective surfaces won't work for this theme, because the scanner makes them appear dull. We're talking about representations of shiny objects, where the reflections are in the photo, engraving, pen & ink, etc. But if you can take a good photo of your shiny collage, where the surfaces have light reflections, then go for it!