
I'll get it started:
*toga with sandals/mercury sandals, and laurel wreath for the head, and a mercury winged helmet
*jeans, cut off jean shorts, bell bottom jeans
*male swim trunks and speedo; female bikini and one-piece swimsuits of various cuts.
*t-shirt with round and v neck, and low-cut neck for female characters
*tank top
*knuckle gloves, spiked knuckle gloves
*ninja costumes (think MK2 and MK3 male and female ninjas)
*cyberninja costumes (think MK3 inspirations)
*regular tights for pants, shirts (long sleeve) with logos centered on the chest, and over the right or left chest
*logo option for right and left shoulders
*costume pieces: shirt/pants that are fabric, matte, gloss, padded, armored (think Batman Begins/Dark Night armoring, comic-style armoring);
*helmets: full bird / eagle helmet, bird/eagle with face open and with mask; full lizard/dragon, dragon/eagle with face open and with mask; mechanical versions of the same;
*gloves: forearm length, wrist length, captain america style folded,
*boots: sneakers, women's flats and heels, penny loafers, dress shoes/tuxedo shoes
*costume sets: tuxedo (male and female, with a skirt option), suit (male and female, with a skirt option), ninja, classic hero (think silver age), mediaeval knight (plate armor, chain armor, fabric covers that drape below the waist, various helmets, broadswords, morningstars, spears, etc); Roman centurion armor; Greek armor; Spartan (300 movie) armor (m/f); Iron-Man-esque/Positron-esque armor sets
*masks: flash, robin styles, full face styles
*eyepieces: various cyclops goggles, two-eyed goggles
*costume pieces: robot arms, legs, torsoes, heads that look like the terminator and various sci-fi robots
*capes/wings: angel wings, bat wings, dragon wings, metallic bird wings, metallic dragon wings, metallic bat wings (think Archangel, and various wing types from CoH); capes: superman style, batman styles, various lengths, one shoulder, two shoulder, clasp, no clasp, corded.
It's late but I can come up with more later, and I'm sure everyone else has some great ideas too.