For the "card" idea, you could make the whole thing out of polymer clay (use a strong brand if you do that) which you could create as one piece or two pieces hinged together in various ways, etc (see the Books page below, or the Liquid Clay page for saturating fabric with liquid clay then using as a long flexible spine/hinge).
Or you could use various kinds of onlays--large or small--on the front or inside or both of a card which was made from cardstock or any other material you want. The onlays could even be "transfers" put onto a thin sheet of clay or onto a liquid clay decal. Or the onlays could be things like cane slices, images made with "slice painting," small molded items, Balinese filigree, decorative sheets of clay made as patterns or using some of the ideas that are used when "covering" items with polymer clay, etc.
Check out some of the ideas on these pages at my site...you can click on them all from the Table of Contents page there (or any page):http://glassattic.com/polymer/contents.htm
....Cards (and artists trading cards, etc):
....Books & Covers (and pages, etc):
....Sheets of Pattern
....Covering (also Eggs, Pens, BOH/bottles)
....Canes-Instruc. > Slice Painting
....Clay Guns > Balinese Filigree
As for hanging polymer stuff from a banner, you could use virtually items you wanted then just hang them in various ways. There are a lot of ways to hang polymer things discussed especially on these pages:
....Pendants > Loops & Holes for Cording
....Jewelry (various categories for stringing, swagging, or putting on leashes & clips, etc)
Or you could just glue or otherwise attach the items to a strip or larger shape of fabric, then attach that to the bottom or center of your banner, etc.