I would look at whats common between both iPhone and Macbook.
Wifi network? Router? Your ISP even? Can you download an image over data rather than wifi to the iPhone?
Is this all images or only some?
Whats the souce of the images?
Can you view them OK on a different device?
If its a wifi network thats common try powering it off, leave it for a coupel minutes, switch it back on.