This probably isn't a sought after idea but I myself and several people I play with on several servers would love to be able to do this. Well, for survival servers there's a hard limit of a base then 6 layers for banner creations. 6 layers doesn't really let you use your imagination for banners. I've made some pretty cool banners in single player mode but can't make them in multiplayer due to a 6 layer limit. Would like to see the layer limit increased. double that maybe? Maybe even add more options like other skulls and not just creeper, dragon and wither skeleton. Maybe a redstone option to make the banner glow or sparkle.
How about a 2 sided banner, currently a banner is just the stick frame with the banner creation on one side, how about the sick frame with the banner on both sides of it so the banner can be seen from 2 directions