The image is in the Menu Left HTML box.
Unfortunately, that box is a “Plus” option which does create an interesting problem as with only the Base Xtreme you have no access to that box.
@weaver, it looks like the conversion plugin converts the Left HTML content to the Base theme even though the base theme does not support it.
Is there any way to remove that image after the fact?
@mattyjames
In the mean time, you could solve your problem by Hiding the left HTML box with the custom CSS rule below, and by adding your new logo using the WordPress Custom Logo found in Appearance > Customize > General option > Site Identity.
Then add that logo to the left of the menu bar using Customize > Added Content > Menus > Add Logo to the Left & Height of the logo settings
To hide the current Menu LEFT HTML add the rule below in the Theme Global Custom CSS Rule box
.menu-primary .wvrx-menu-html {display:none;}