There is currently a bug on Clan Pages where the banner does not display on the Clan Info tab. Clan Pages are very buggy and outdated as they are, but hopefully, this will be looked in to and fixed soon.
It appears as it should on other tabs for me: ~ Sicariu
Wont update on RuneClan either which is something a lot of clan leaders and members even use to track their Xp gain and their Clan, friends.. etc. Please fix this. It's something minor but its not a fault on RuneClan's side as they receive all their data from here.
Frankly we're super busy with ... literally everything.. right now, hence why we haven't replied sooner.
The problem is a caching issue on our side not refreshing the banner, unfortunately there's not a solution I can give you that I'm aware of. Further, this isn't something that's going to be fixed for some time.
If there are any more updates or I'm corrected by another JMod I'll let you know. Until then I'm afraid its something you're going to have to grin and bear.
Apologies, Mod Lyon Unfortunately, it will probably be awhile before it gets fixed. ~ Sicariu