Personally, I like the old B-movie quality Cybermats over the "Bitey" design in Matt Smith series. Here's my attempt at something in this style -- with full credit given to http://myuntemperedschism.blogspot.com/2012/01/1967-cybermat-on-budget.html for the brilliant idea of using a plastic scoop for the main body.

As can be seen, I did the "teeth" different than in the above link (shorter, less splayed) and I really should've used a sharpie for the eyes rather than try to paint the designs on...