Herdware is absolutely any personal 'decorative' item or product which may (or may not) have been genuinely cool, fashionable or different once, but is now overwhelmingly "me too" popular, and cliched to the point of banality, or simple embarrassment.
Often favored by teens - Mall rats
easily spring to mind - & young adults wanting to project belonging to a group, culture or common state of mind, herdware can include the ubiquitous naval, ear, nose, lips, genital or etc, etc, body piercings. Or out-of-the-box tattoos like Celtic, faux-tribal, barbwire, etc, ad nauseum designs.
Types or styles of clothing, jewelery, cellphones, and any other hackneyed device, appliance or conveyance can devolve into herdware.
The group gathered every Saturday evening and flaunted their herdware at one another and imaginary admirers.
With her herdware of fresh tatts and piercings and dangling ipod she felt she was the coolest teen in the mall.