Able to put images behind tasks and subprocesses in a diagram

Hi!

We are using Bizagi for doing rich process diagrams in these diagrams users would like to use pictures. On these pictures they would like to put taks and subprocesses. However it's not going to good for us. The tasks get hidden and put behind the picture and especially when publishing the diagram to the web. So for example you have a picture of a factory and would like to put tasks/subprocesses on that picture to show where the process/activity is taken place.

Again, today it's almost possible however the tasks/activities get hidden behind the picture. Attach a file where management wanted a nice "gray box" behind the main processes (in this example renamed to not reveal business secrets).

So would it be possible to have a kind "Move Backward" like in PowerPoint when having multiple images?