I always design with vector shapes. But the details are lost when you scale them down. For example: you have made 512x512 icon with lots of strokes and shadows for details. When you scale it down, style wont change. But thats not the problem cause you can resize it by percentage. The problem is when you scale it down to 32x32 or 16x16. Most of details wont be visible. I read somewhere that it is recommended to make icon in many sizes from sratch. But I still dont understand why I am so sad about that, since in DA gallery folders I wont need any scaling I guess..
Yes, you are right, when you scale something, even if it´s vector, you have to change the size, it doesn´t have sense to have a 50px shadow in 128x128 icon while on a 512 could be ok; you always have to apply percentages,the technique of resizing in most of the cases could be applied at least to the 64px icon, but the smaller sizes: 16,32 & 48 is better to draw a new icon, applying a lot of pixel work.
In your case of the dA gallery folders is true, you only need one size so.. don´t worry about scaling Regards!