I'm one of the developers responsible for building this Visualizer (it was actually me and one other fellow handling the backend stuff).
For anyone interested here are the techniques I had to use to make this project possible. There are no pre-rendered images in the entire visualizer, it actually used Flash to warp a tiled texture with a displacement map, it then applies a mask and specific shadows to create the final rendering. Each component of a suit has its own mask and a corresponding xml file to give it information such as the angle to place the texture. This was done to allow the lapels to go both directions (giving the visualizer a real nice look) to allow for the cuffs and coats to be created without needing to touch the Flash app once it was compiled out. jQuery is only used for the user interface otherwise its a completely custom Flash application. The UI interfaces with the Flash app through some flash vars. Thats it! Nothing too special just a lot of long hours and hard work making all the different combinations (over a million if you don't count thread colors) possible.
I know this is old, but thought I would at least share for the next poor fool that attempts something like this.
Oh and you can totally do something like this in Canvas (webGL would be even better if you can get all the models).