Nightmare: Candy
Design:

There is a spot on the back that can be used to have one of the wings through it, while the other side would have to have to have a hole so the second can fit. The whole would have a zipper that comes down from the top and unclips at the bottom, like a jacket. That way the wings can be slipped in without any harm to the user. There would be no issue for those with horns, as there is nothing on the head to worry about. For those with tails, a hole in the back could be made to accommodate for whatever size tail there was. The Fey would have a special hole made for them to use for their flower, soft fabric being used around the hole so it wouldn't be hurt. Those with special legs, like the baphomets and grimm, would either have to have a special pair of boots made, or not wear them at all.
RP Response: An outfit that would work for all the races? Well that would be impossible without making a special outfit for each race. Now that the daydreams had arrived, it was going to become even more difficult to make clothes for a broad audience of needs and also wants. The only thing she could do is think up an outfit and think of all the ways she could change that outfit to fit all the different races' needs. Then, if she ever decided to open up her own brand, get feedback from her customers on how she could better make clothing that accommodated to their needs.
After deciding on a top, shorts, and boots, she got to work making those elements unique in their design. The shirt ended up going under the shorts, which has slits at the sides so one could see the shirt underneath more. The shorts also had a white gem near the top above the slits, being able to connect to the boots through straps. For her special touch to this outfit, she decided it needed to be sparkly like her last outfit. There was something about glitter and blue that spoke to her this cold season, and she felt the need to have that be in this outfit as well. Now it was time to think of how she could approve upon it to help the other races.
Hmmm... the top could have a hole in the back with a zipper like a jacket so the side that wasn't bare could still fit wings for the fey, chimera, and fallen, and also have a hole in the front for the fey's flower as well. Not only that, but the hole for the fey on the front would have to be soft and safe for them. For those with tails, like the demons, grimm, nixie, goblins, and so forth, there would be a hole in the back of shorts that would be custom for each tailed race. Candy knew each tail was different, and each needed to be specially shaped so no race was left out. For races with horns she didn't have to worry, as her outfit had nothing on the head. The feet however were the problem that caused her the most trouble. How could she cater to those with feet that were not the normal sizes or shapes? All she could think of was possibly making special boots for each race that needed it, thinking mostly about the baphomets and the grimm, but then again if those races wanted they could go bare foot? That could work right?
With her project finished, Candy made sure all her designs looked good before presenting them to her teacher. Hopefully this was what was meant of her for this assignment. It had been a rather hard one to come up with ways to help each race fit into her outfit, but Candy felt it had challenged her to keep other races in mind when working on outfits. Maybe her next goal would be to try to accommodate for those with mutations? After all, her own daughter Phyre was a mutant as well! Who else would focus on those in their society that were not in the norm and needed special care in their clothing more so than anyone else?