Maybe you could go the composite route?
1. Shoot an image of the clothing on a person, against a white background will make your post processing easier.
2. Shoot an image of the clothing on its own. You are mainly after the bits that are hidden, like the back of the collar. Take care to use the same lighting as with the first shot.
3. Combine them in editing software.
Alternatively, you could use a wire mesh mannequin and clone bits of it out or stuff the clothing with fabric or foam to make it looks like someone is wearing it.
I'm currently working on a new website, but I've got some images on flickr
that you can have a look at. I've also been known to waffle a bit on twitter