Originally Posted by Adam Smith

You can put a link to an image anywhere. Can be hosted on image hosting site, FT, your Dropbox/Google Drive/whatever.

We've also had a number of FT users comment that posting large images can be painful because (a) it can require excessive vertical scrolling, and (b) it can chew up a lot of data for those on mobile. Those issues can be solved by resizing images to be smaller, but that also makes the menu less nice to look at for those who want to see it in detail.

Hence my suggestion to upload the image to a sharing site and put directly in the wiki as opposed to posting in the thread.