I’m using RW6 with the theme called Split that came bundles with RW6. RW7 improvements list says something about being able to change the banner as being improved. So is it easier to change the banner graphic with RW7 then and is the Split theme still include? Dealing with the code is too much for me to deal with I think.
There is a write up here:
https://www.yuzoolthemes.com/support/article/view/themes/split-theme-banner-images-101
About handling banner images in Split theme. Take a look, its not too bad once you get used to it.