Wikipedia has some nice vowel charts, available at https://commons.wikimedia.org/wiki/Category:SVG_vowel_charts.
Example (Korean vowels):
Example (Australian English diphthongs):
Similarly, there are vowel and consonant charts in tabular form; Markdown doesn't seem to support tables easily.
Example (Ubykh consonants):
How should we produce charts like these and use them in Markdown? While it's possible to take screenshots as I've done here, that is hard to use, and hard to edit the output, so it's not a good solution.
I see that the UX Stack Exchange has integrated a UI mockup editor. Perhaps something similar could be added on Linguistics (and maybe the sites on specific languages).