To my mind costume jewelry is a step above your 'junk' jewelry description. I'm saying gold plate, silver plate or silver other than 925. Semi precious stones such as agate, coral, hematite, jasper. And of course the rhinestone types. And I guess you could include man made like simulated diamonds (CZ's).

Fine jewelry can also contain semi precious stones but tend to be of the higher end of those. Such as, amethyst, apatite, aquamarine, citrine and garnet to name a few. Stones that are hard enough to set with prongs and hold facets. Therefore, worth the effort of good metal work., and are usually set in sterling or 10k gold

While you may refer to your items as junk jewelry, they will sell better if you call them fashion jewelry.

The man called them junk. I advertise it as "costume" jewelry, which many people seem to think is actually fine jewelry, but you don't know it.

I think your description was accurate except for the mardi gras beads which I would also categorize as junk-fun, but not costume. To me costume is indeed jewelry made in imitation of fine jewelry with fake gems, etc.. I wonder if the term originated with stage jewelry that was made for actors' costumes.

Costume jewelry is inexpensive but "fashionable"...not gold filled, not semi precious stones unless they are in "gold toned" settings.
Costume jewelry is from companies like Coro, Monet and some of the Krementz line....as well as other unnamed faux gem makers.
Most "junk" jewelry is costume, but all costume jewelry isn't junk.

The collector's version of "costume jewelery" is the vintage stuff made of sterling silver and good gold plate or 14-18k gold filled with nice design and good crystal gems.

It's light years above mardis gras beads and the stuff from the dollar store.

Here's eBay's definition of costume vs fine jewelry. Note that sterling silver is not classified as costume jewelry.
http://www.ebay.com/gds/What-Is-the-Difference-Between-Fine-Jewelry-and-Costume-Jewelry-/10000000177633017/g.html