Image loading slow from server, is this normal?

I am doing a coding challenge, and they gave me an api which gives me posts, those posts contain images.

The images are links to lorempixel.com

Those image links take a while to load, and some timeout after a while.

The whole lorempixel page is slow, do you think this is on purpose?

Also, some images wont even load.

example of image: http://lorempixel.com/640/480/city?61610

"images": [
      "http://lorempixel.com/640/480/city?61610"
    ],

Do you guys have any idea, how I would solve this for this challenge?

Thanks.