I asked about linking before and it's ok to link them directly:

https://www.themoviedb.org/talk/556fbb0a92514140ca0005af

Not sure about your other question, sorry.

@MaFt said:

I'm looking at making use of the TMDb poster API but I was wondering how it works. Are we expected to download the images and host them on our site or are we OK to link to them on the TMDb servers?

Indeed, the discussion @strig linked to should answer this. If it doesn't let me know.

Also, is there a way to request multiple results in a single API call so I could get, say 5 posters in one go instead of 5 separate cURL requests?

No, our image and API services do not support this.