I put in a support request about it and was instructed to link to some examples of entries with broken images/videos, so I decided to compile a bunch of images/videos (some that were in my earlier entries, some not) into one entry so I'd only have to link to one.
Random examples of images in my ScrapBook: (NOTE TO SELF: leave these as the LJ copies of the images even in the DW version of this entry, so that I can test LJ images in DW entries)
Random examples of images hotlinked from other sites I visit:
A couple of the videos that wouldn't show up:
...All the images and videos in my journal are showing up today, apparently. Oh well, at least I have an entry like this in case there's a similar glitch in the future. :)