I think there are some really good series that only got one season in the UK (which is usually six or so episodes). Some you might be able to find streaming, I'm listing ones that are good inspiration for RPGs. Some examples
Ultraviolet (1998) - Cop discovered a government backed vampire hunting unit after his partner goes missing, starring Jack Davenport and Idris Elba.
Apparitions (2008) - Father Jacob a priest that vets miracles to see if people are suitable for sainthood, gets involved in an exorcism and a battle between good and evil.
In The Flesh (got two seasons! 2013/14) - Flows a recovered zombie, trying to adjust to life after the apocalypse and the discovery of a cure.