Images load if the URL ends in an image extension like .jpg, .png, etc. Otherwise gossip doesn't know what it is (it doesn't download every link and check, that would be madness). So it shows SOME images, but not all.

If you compile it yourself you get videos too with ffmpeg. But videos require a lot of system libraries of very specific versions and so it's very hard for me to include that into release packages as my compile won't work on other people's systems that aren't precisely where my system is.