I am following the episerver documentation to add display width options to blocks.
When go to add a width to a block the icons are missing for each width, why?
Have you checked to make sure the images you are referencing (epi-icon__layout--full for example) exist and are referenced correctly?
Are you working with the sample site or have you created your own site?
EDIT: There should be a png called layoutIcons24x24 under "Client Resources > Images > icons" if using the example site and default icons.
I'm assuming the icons are added through the class, and sense this is built-in epi functionality i would expect the classes provided in the documentation to be part of the epi css.
So there is the css class "LayoutIcons.css" which references "../Images/Icons/layoutIcons24x24.png" as the image source which is the sprite sheet for these icons. (At least this is the case in the Episerver Alloy Template).
Can you double check that you have both the LayoutIcons.css and layoutIcons24x24.png files, and if these are in place that they are referenced correctly where appropriate.