Our marketing department is not afraid of asking for help. They ask for help on a lot of things, which is not a problem, as longs as it is not about images in Prismic... again... That's why we hired a 12 year old to do some research and write a definitive guide on images in Prismic. These are the results:
Uploading and selecting images is easy
Resizing an image is easy
Resizing the grid is a piece of cake
Constraints are annoying, if you don't know they are there
The buttons at the top are awesome, if you know what they do