This is an idea that pops up regularly, but makes no progress. While the code side is not difficult, it covers a lot of territory as portrait and body images appear in many separate locations. The current mod system cannot easily support it, so generally it would be done as a patch instead. That said it takes quite a bit of knowledge to implement so there are few who would be capable of doing.
The biggest challenge is providing pictures. There are almost none who have the time and skills to make images for the game for free. It is tedious but relatively easy to find the random full images off the internet. It is quite difficult to get partial images that can be interchangeably applied to multiple partial images. So while the code could be created, securing even a single set of images is quite difficult. We rarely get people who can put together a normal image pack, so it's hard to see us getting more than one dynamic image pack put together.