How does one set the thumbnail for what their wiki looks like when searched for on community.fandom?
For example, a search for Star Wars produces a thumbnail for starwars.fandom on the right. I can see that it's using w:c:starwars:File:PediaBIG.png for the image, but I don't know how community.fandom knows to pull that image up for the search thumbnail.
It used to be File:Wikia-Visualization-Main.png but that doesn't seem to be working anymore.
Since community search is a new feature, there probably isn't any public documentation yet. At least, I can't find any. What I can say is that is seem like File:Wikia-Visualization-Main.png is still being used for most wikis. So perhaps that is the default unless you change it? Regardless, since there is no public documentation, it would probably be best to ask staff directly. If you do, could you post their reply here?
Okay, so after some searching around, it appears to just use the standard promotional content as set by the mobile main page editor (see here). However, since only admins can see what is set for this, I cannot confirm that this is indeed how the Star Wars wiki has done it. All I can say is that this is what gets used for the wikis I admin.
Hm, I don't think that's it. You pointed out an option I hadn't considered (I didn't even think to look in the mobile layout). I just tried it on a test wiki, gave the cache a little while to refresh, but didn't have any luck. Also, the existing description didn't match what I saw coming up in search.
Thanks for the response; I think you're right, I'll contact staff directly.
My understanding is that it's supposed to use the image and text from the 'Promote your wiki' of the mobile main page tool, but there is some murkiness about how this is actually working (and there may be some very heavy caching involved).
It's something I've been looking into recently, and I'm working to try and clarify the situation. If/when I have an update, I'll likely see about noting it on a Tech Update post.
FWIW: the Wookieepedia mobile main page settings and the search result closely align.
I have one other place I can ask. I will update here if/when I figure it out.