Another question about Equal Column Lengths and the contentWrapper Background

After searching and reading several topics on this, I did find out that with the Equal Column Lengths checks, I can't insert my own contentWrapper background. My work-around has been to replace the image with my own after the page is created, but I like having as much as the final layout complete in the preset as possible.

So it seems that equal columns are not possible without the BG image in the world of CSS, but I don't understand why that is - it's a background image, not inserted as content.

What are the pros and cons of using equal columns? The one thing I notice is that the overall layout seems more stable and easier to work with.

I also read that the default image used is "created" when the equal columns is checked - is that true, is it actually created according to the set background colors, or is it merely using a pre-made image that goes with the theme?