@xileets As mentioned above, all were made by our ‘Wizard of the Graphics’ @shizzlemetimbers . He got that exclusive title for a reason. 
Here a thread with all banners he made thus far.There have been maybe two or three other banners (usually made as jokes and/or for specific birthdays) that were made by other members. Here one Scott made for Train’s birthday in 2019 for example. (EDIT: correction: @trainofthought made the banner himself, but Scott put it up as surprise later on.) But apart from those exceptions, it’s all Shizzle’s amazing work. 
Greetz,
Quuador