I fired up S.2.38 on the BDP-2 with the slightly old Pale Moon 26.5 browser on Windows 8.1 and right away fell in love with the background image feature in the default view. It seemed like a delightful bit of decoration and added visual interest that I expected to miss if it were ever removed. The background image was in focus. However, when looking at it with up to date browsers on Windows, macOS and Linux, it's now clear to me that it was intended to be very blurred and essentially unrecognizable. I don't have much love for blurred images used in this way although I won't say I hate the feature but I definitely don't like it nearly as much. You can see that for me it would be wonderful if the option existed to present the background without the blur. BTW, I have no idea where the images come from but I actually don't mind that. It adds a little more fun to the interface.
If you add this option, I'll be eternally grateful!
Edit: After playing with this for a few hours, I've recognized the obvious fact that the particular background image displayed is a very significant variable that determines whether the overall effect is pleasing or not so much. (I've been looking back and forth at the two computers and comparing with and without blur.) When set to the Crystal Theme, more of the image is visible and the overall effect with the blur can look very nice.
In the end, I would say that if you're very reluctant to add too many items to the customization menus, just adding the enable/ disable option as you intend to do would not be a bad compromise.
It occurs to me that allowing users to select an image much like a desktop or perhaps a series of them, might be a popular alternative. In that case I suggest the blur should be optional.