I want to make a bunch of designs in Inkscape for a Tshirt company I'm starting. But don't know how to do what I'm trying to do.

How do I do designs that would be like brushes in Gimp or Photoshop in Inkscape? That would go around an image?

I added a picture of what I'd like to do.

Well to do what you want to do then you have to create a few different layers one for the t shirt image, then you need to trace the image so it is a vector shape in a layer above the image set this layer to muliply and align it over the t shirt changing the colour of this vector shape will change the colour of the t shirt. copy the vector shape and paste it in a layer above place the design on the t shirt that you want and then use the copied vector shape to place on top and mask your design so it doesnt over flow the image. Then you need one more layer above and this layer will be for your creases in the t shirt so draw on the creases and blue them a bit and change to opacity so you can still see the design.. if you like you can add an high light layer to

But thats pretty much how it works by the looks of it