
One useful approach in working with cast-offs and items of unknown origin is to look at an item for what it can be, not what it was. Turning an item upside down often initiates "eureka!" and then I am off to my studio. Here's a recent project that demonstrates what can done with minimal effort and a modicum of creativity, giving maximum results.
These are three glass coasters that either came from Goodwill or out of a "free Box" at a yard sale. The two square coasters were hefty and had a substantial lip on them, the round coaster was heavy as well...paperweights came to mind.
If the square coasters were turned upside down, there was an open cavity that could be space for a 3-D collage. I started to collect what I might use in my collage...
a stash of old keys...
a mixture of orphaned buttons...

combined with some leftover wrapping paper, a few stray feathers and a snippet of ribbon...
the end result!
close-up of the first square paperweight with stamp, button and feather as the design elements.
close-up of the second square paperweight with stamp, feather, old key as design elements. I added a sealing wax impression for some extra color.
close-up of the round paperweight. This one I did not turn upside down to use the hollow space for a 3-D collage but kept it as a coaster - making a 2-D collage under the glass with wrapping paper, dictionary definition snippet and a very light feather. The idea of having it be a paperweight with using the coaster indent to hold paperclips or magnets or whatever else you stash on your desk appealed to me.
All three paperweights are for sale at my space at Faded Elegance. Since I use original elements in the design, these three are unique and can never be exactly replicated again. Start your own collection of stray items- tear off the stamps of letters you receive, clip the buttons of a worn shirt before it is tossed, cut out interesting photos from that magazine before it is recycled - you might be surprised at what you can make from this junk!