Basically this is Costume Porn applied to a cape (or robe worn like a cape), where that piece of clothing is expensively decorated. This was common throughout history, for both men and women, as capes of various kinds were a common clothing item, and clearly visible due to their size. Thus a grand cape would easily be a way to show off one's wealth and social status. In fiction, it's a way to either show the same for a high class character, and/or for the artist/costume designer to show off.
Now how decorated a cape can be will vary. It can be trimming just part of the cape, to lining it, to entirely covering it. What is decorating the cape can also vary. Real Life capes can be decorated with Fur, embroidery, gold, and even expensive dyes can count. Fiction can decorate them even more, from metal and armor, to Tron Lines.
You might think pimping out a cape would be easy, but capes are a lot of material to work with, and even just edging one will take several yards of trimming. And of course historically all the decoration was done by hand. Thus anytime you see a cape where there is some kind of fancy trimming, lining, decoration, or other kind of work done, it counts as this trope.
If this cape is worn for protection, it overlaps with Stylish Protection Gear. If royalty or nobility wears one, it usually is part of their Requisite Royal Regalia (and why the trope Ermine Cape Effect is named so).
Now let's make it clear that the cape itself has to be decorated. So even though Superheroes Wear Capes, the majority of their capes will not count as this trope (even for the villains), as those capes are usually simple, no matter how cool or flowing they may be.
- Batman's cape counts in the continuities where it has a mechanism built in that turns it into Cape Wings.
- Ordinarily, Wonder Woman does not wear a cape. For her, capes are more like what they are for most people—an unusual sort of formal wear. So when she does wear a cape, it tends to be a lot more pimped-out than your traditional superhero cape.
- Captain Marvel of Shazam has a cape with gold edging.
- Doctor Strange has a particularly magnificent cape, made out of bright red material with fancy golden trim that merges seamlessly with a matching golden mantle and topped with a resplendent, distinctive (albeit ludicrously improbable) collar. Seriously, just look at that thing! Fortunately it's also useful—it's his Cloak of Levitation and enables him to fly.
- Belle's winter cape in Beauty and the Beast.
- The Disney Princesses have a few as part of their "Happy Holidays" Dress sets, including a set where their capes were trimmed with Gem-Encrusted white fox fur.
- In The Care Bears Adventure in Wonderland, both the queen and princess of Wonderland wore ermine-trimmed capes, but the queen wore one that was trimmed with red hearts.
- Megamind, with much fanfare, dons a cape for battle with gargantuan spikes on wide shoulder pads and the high collar to end all high collars called "The Black Mambaaaaaaaaaaa..."
- Gorgeous George was the first wrestler to use the pimped-out robe variation. Ric Flair is a more recent example.
- The generals in Dragon Force (video game) wear capes that are not only fancy, but float just above their shoulders.
- Rosa's outfit in the remake of Final Fantasy IV is actually two capes, a lace one worn over the regular one.
- The leaders of the Three Kingdoms in Dynasty Warriors 7 all have ridiculously ornate capes, each one etched with a design representing their kingdom in extreme detail; Liu Bei with a dragon, Cao Cao with a phoenix, and Sun Jian with a tiger.
- Merlina's embroidered robe in Sonic and The Black Knight.
- Jessica Alkirk of Lunar: The Silver Star. See here.
- Skillcapes in RuneScape have large, ornate shoulderpads, and lots of trimmings. The Dungeoneering Mastery Cape even includes a magical smoke generator that makes smoke trail behind you when you walk.
- Taken Up to Eleven with the Max/Completionist capes. They are fully pimped out, trimmed to the max capes with aforementioned smoke generators, and they are even color customizable for max pimping. Of course, the requirements to get one are quite extensive. (The max cape requiring you to reach the max level in all skills, Trimmed Completionist is well, 100% Completion )
- King Ladekahn, Queen Corellia, and Lady Melodia of Baten Kaitos.
- Touhou: Utsuho's cape is decorated with an independently scrolling star field.
- Ghetsis' cape in Pokémon Black and White is pretty pimped-out.
- Of course many coronations have these. The capes are usually decorated with gold, ermine, or both (see the coronation pictures of Elizabeth I and Russian Tsars).
- In the 1930s, to about The Fifties, at least in the US, short shoulder cape of white ermine was a popular garment for young society women 18. Thus movies around the time used it as a way to identify these characters as such.
- Liberace was famous for his flamboyant capes (no pun intended).
- Polish Husaria wore a leopard skin as a cape. That is automatically awesome, all the moreso when it was worn over the more typically impressive red and gold cloak and steel-and-gold armour.