Hi, I will guide you how to create a megamenu.
1/ Click Navigation in admin
2/ Find Main menu and click on it. http://prntscr.com/ktkg8n
3/ if you want to create a menu which have many sub menu. And each sub menu will display on a column.
you need to insert [megamenu] in front of item menu. Example: Pages[megamenu]
+ http://prntscr.com/ktkhcx
+ and then create a new menu which is called Pages[megamenu] : http://prntscr.com/ktki4k
+ Next, you need to create other new menus which is called Home, Blog pages, Inner pages and Collection pages
http://prntscr.com/ktkj34
http://prntscr.com/ktkjcs
http://prntscr.com/ktkjm0
http://prntscr.com/ktkjw4
And here is result : http://prntscr.com/ktkk93
we had a mega menu with 4 columns
4/ About mega menu which have background image.
You need to insert [megamenu_image] in front of item menu of Main menu: http://prntscr.com/ktklgb
And then click Edit button and insert link image: http://prntscr.com/ktklpu
http://prntscr.com/ktkm3m
Notice: syntax of link image: #+url_image
About sub menu of this option, you can make simillar with mega menu situation
Regards, Andy