"Doctor Who" has followed many different conventions for naming new alien species. Sometimes it's been adding "oid" to various word parts or random syllables (Krynoid, Mechanoid), sometimes it's been putting together something that just sounds cool (Dalek, Forest of Cheem), and occasionally it's been taking potentially-appropriate words from science and adapting them (Silurians, Adipose). I've collected a small list of other science terms (mostly biological) that I think would make good names for Doctor Who aliens. Steven Moffatt, you can thank me later.
Feel free to add your own!