I know that the tag excerpts are prime real estate, but I think it would be nice if we had the option to add a small product icon/graphic to the excerpt.
Here's how it looks now:
And here's what I was thinking:
To make the tag wiki excerpts uniform, you could have us upload an image separately (like: "Choose the excerpt image, no larger than 80px"), rather than letting us put the image in the markdown - this way, you don't have to modify the "no markdown in excerpts" rule.
I would also think a size constraint would make sense - in my example above, I used an 80x80 icon (which only adds a single line to the excerpt, not using up much extra space). For cases where there is no icon, you could use a muted version of the site icon as a placeholder (or just a blank, white image).