Not the best models for converting but you could give it a try. What kind of bits do you have available to make them caosy?
Here is what I would do to make the terminators chaos terminators:
Drill in holes on the shoulder pads. Insert spikes that you get in all the chaos vehicle boxes.
Swap terminator heads for chaos space marine heads.
Swap out the storm bolters with 2 bolters glued together.
Scrape off all the aqilas.
Freehand chaos symbols on any surfaces that feel too plain.
I also have converted some terminators into obliterators. Here is a pic (nevermind the paintjob, it's ancient):
As you can see I just slapped on as many weapons as possible, used some green stuff for the flesh and used some chaos bits to make him, well, more chaosy.