Regarding anything creative, things can be shared directly on the Fan Creations forums, that's probably the best avenue for that. Art can also be tweeted to us, we will like/RT some of it as well (we obviously cannot like or RT just about everything). When it comes to guides or useful resources for the Community, we got that thread (which is a bit outdated, but we can dust that off!), feel free to link your pastebin to me and I'll be able to add them there too.
I am not extremely keen on having banners on forums / signatures. Keeping the place as readable as possible is our first priority, even if it may look a bit stale. Regarding colour template/design anyone is just free to make their custom CSS and use an extension like Stylish or Stylus. If someone comes up with something amazing I wouldn't even mind sharing it publicly but it will have to remain something "unofficial" through an extension. For brand image reasons we have to keep the default design as it is, it's not something we can change on a whim. (However if you feel that something is difficult to read due to a bad colour scheme, as long as it's something minor it's an adjustment I can make instantly).
Regarding the Avatar Gallery and forum upgrade, I just asked the team in charge again today for an ETA. It's a feature we know works since we have it on another NCSOFT title forums, so all we need is to deploy that update on Blade & Soul forums.