There are several ways to add images to wiki. The prefered way is to embed them in an HTML element after uploading the image to the assets folder. An older way is to use embedded images that are base64 encoded into the page.
VIMEO 257485333 A short video tutorial about how to add an image to Fedwiki.
# The new way
To add images to your site use the About Assets Plugin (below) to upload an image to your sites asset folder.
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Once the image is uploaded you can open the image in a new tab, and then drag and drop the url of the image onto the Imagine Transport.
To be more specific once you have clicked on the "upload" button above, and have selected an image from your desktop to upload, you will see it listed in assets plugin above. Next, by clicking on it's blue link - open the recently uploaded image up in a new tab.
Finally drag and drop the url of the image onto the imagine transport in order to create an html image item you can drag and dro onto a page of your choice. I usually place this imagine transport on the welcome visitors page for easy access (you may need to scroll down).
POST https://rest.livecode.world/imagine
Often you will want to open the ghost page of the transported image item too the far right of the lineup so that you do not remove the other pages from the lineup.
# Embedded image