[Looking at supersize / extended size clothing which is to say, clothing I can wear. Preferably modeled by fat people.]
I’ve done different things for Halloween. One piece is the Love Your Peaches catsuit in black velvet. I bought it for clubbing, but it (or black leggings and top) can be the basis of many a costume. Get cat ears & a tail at a costume or craft store, a pair of black gloves, and presto: cat costume. Add a black ski mask and you’re a cat burglar. Find a cape and mask and you can be a superhero. Hang a few whips and handcuffs from your belt and you’re a dominatrix. And so on.
I did a goth outfit one year: long black wig, black slacks, black velvet top, black nail polish, and a deep blue lipstick that made my lips purple. (The clothes and black shoes I had, just not the wig and makeup.)
I’ve also done variations on the standbys of witch (long black dress, black pointed hat), gypsy (colorful clothing, scarves, jewelry), and toga (white sheet ;)
Roaman’s does have plus-size (but not supersize) costumes.
Do you like to dress up for Halloween? If so, what costumes do you favor?