It takes a while for recently approved covers to show on games' rap sheets.
Well I can see the front cover for Dragon Ball: Daimaō Fukkatsu now. So I guess that the site builder needs some time a notice that new content is available from the database. Unfortunately mobygames hardware and internet connection are not high-end.
Hmm, I can't, it still says "There is no NES cover art on file for this game", maybe I'm connecting to a lagging server that is behind or something...
Or you're connecting to a subdomain, other than the NES one.
As a matter of fact, it still doesn't show for me.
Weird. Looked just fine for me from the start (if I change the subdomain instead of just clicking the link of course, as my favorites get me straight to pc.mobygames.com).
I've been viewing the site thought www.mobygames.com the whole time (the entry is now correctly showing a thumbnail for me now btw).
Sometimes they show up right away, sometimes it takes quite a while. This one took over a month to show up on the game page, but others approved in the same batch appeared immediately.