Background picture in New Window

[#1]

I am working on modifying an existing dashboard consisting of a single window with multiple tabs inside. Each tab has a variety of hlistbox, vlistbox, outline boxes, etc. I am trying to simply add a picture behind the current grouping of boxes in the window but I cannot seem to figure out how. For pictures normally I just use a simple picture box, but I am not sure about how to send it to the back behind everything else. Any help would be appreciated. Thanks!

[#2]

This may not be the answer you're looking for, but I hope it gives you ideas.

I just tried bringing a report into Application Builder, added a PictBox, and gave it an image. By default, items are overlaid on top of each other. I found that the item I resized last ended up in the back, so I placed the report where I wanted it then stretched the image to fill in behind the report. 

Here's a picture of a bubble plot over a highly stretched image: