Since there are many (unknown) actors on TMDb I would suggest to fetch the list of popular people first with

/3/person/popular http://docs.themoviedb.apiary.io/#get-%2F3%2Fperson%2Fpopular

You will receive a list of about 250 persons, divided into pages of 20 each. Fetch all pages and put them into one large array (but mind the request limit. Maybe cache the results.)

Then randomly select persons out of this array. The list will contain actors as well as popular directors/writers, because there is no information like "person x is an actor" in the database. It would't make sense, since it differs from movie to movie. An actor on movie A could be a director on movie B, or vice versa.

I hope this helps and I hope my info is correct, since I started using the API only a few days ago myself :)

When I put the following URL in the browser I got the NOT FOUND page:

http://api.themoviedb.org/3/person/popular/550?api_key=xxxx

I'm sure I provided the right key

There's no id to provide with the popular method. To query for a person, use:

http://api.themoviedb.org/3/person/550?api_key=###

vanrundam, use this URL: http://api.themoviedb.org/3/person/popular?api_key=###

You can get the second page like this: http://api.themoviedb.org/3/person/popular?api_key=###&page=2

It returns me this:

{
  "adult": false,
  "also_known_as": [],
  "biography": null,
  "birthday": null,
  "deathday": null,
  "homepage": null,
  "id": 550,
  "imdb_id": "nm0865189",
  "name": "Jennifer Todd",
  "place_of_birth": null,
  "popularity": 1.4,
  "profile_path": null
}

"profile_path" is where the image is normally kept. Because that is null, that means there is no image. For your app, I would skip that entry