Greetings Xiola!
As mentioned, its not about featuring specific artists or desingers.
In a more organized manner, these are my personal suggestions:
1) The banners do have a tendendy to limit themselves most of the time to fashion in a very limited ethnic diversity in humans (and its very rare to see a fantasy avatar or sci fi as the main banner). If human avatars are to be featured it would be great to see some of the outstanding variety out there. SL variety goes way beyond humans...the imagination is the limit. This is not reflected really on the banners.
2) How about changing it sometimes for a banner focused on a nice scenery with a fantasy or sci fi avatar outside the standard "look what I am wearing" or "I have a grill". Something themed. Here, out of hand, are at least 12 themes or subcultures I cant think of:
-Fantasy, Medieval Style -Cyberpunk -Regional (Country Cultures) -Modern Art
- High Fantasy -Sci-Fi -Furry -Horror
- Steampunk -Dark Sci-Fi -Animal avatar users -Period Themed
-And of course, fantasy fashion and high fashion, which are well represented already.
And I did not really think about them, there are 10s more, all represented by gorgeous views and designs.
Of course, no adult subcultures themes mentioned. SL has its adult side too, but, like in RL countries, there is a red distrcit and people who are looking for it will find it. Its more really about giving an impression of how compex and diverse SL is. Having always the same fashion shots gives a very limited vision of how rich SL really is.
Although I understand why RP sims or Charity organizations are difficult to feature on the banners, nothing forbids shots being taken and featured when good enough. If the viewer wants to find more about who, where, why, that can easily be done through a link. In my opinion, its more about giving an idea of how diverse and gorgeous SL is.
I hope this helps clarify my point.