I hope this hasn't been brought up before, if it has just add me to the list of people who would like it. 🙂
I would like to see just more "basic" costume pieces and patterns added, stuff that feels like it should be there that aren't, like necklines that aren't plunging Vs or turtlenecks (i.e. like a crew cut t-shirt), or just a basic horizontal top stripe for boots, or a pattern that allows you to color just the shoe part of tights that doesn't require you to have to use tight pants to fake it, or to be able to color it to make it look like a short boot. I know making whole new costume pieces is hard (like actually having short boots), but just some more "normal" patterns would be very useful. Same with just having some basic patterns for the tops, like having a pattern so we can color the neck/collar area without that also meaning we have hole patterns all across our arms and back too.
Too many of the patterns from the original game are overly designed, so if you want a chest stripe you end up also having stripes across your arms or something like that, or if you want a top horizontal stripe on your boot (that's not using the rubber boot which doesn't look like tights or might not match the style you want and also can't be given different heels) you end up having to use the sharp spike that goes down the boot. In a similar vein, having an option for tight pants/pants that removes the pockets/zippers/lining entirely so they have a similar texture to tights would be useful too (so you can make bottoms with wide cuffs that don't look like cargo pants or jeans or motorcycle leathers, e.g. loose yoga pants or women's disco pants).
Having some more variation on the skin tops would be nice too. I know this is because of the limitation of the original character creator where tops with skins don't allow patterns on them because they couldn't guarantee where the clothes would be on the body, but I think adding a few variations to things like the t-shirt or tanker tops where you have patterns on them (like a circle in the center or a stripe down the middle, etc) would be really cool and used a lot by people.
Players have gotten really good at getting around the limitations set by the original character creator, but I think it would help a lot to get some just "basic" things added like the above and similar (just simple lines on the edges of tops/pants, single stripes or blocks of color that don't extend all across the sleeves, etc).