I use a square (without borders or borders the same colour as the fill) and place it over the areas I wish to remove. The square should be the background colour. Complex shapes can require a lot of the squares. Once finished (if the graphics program I am using supports it) I flatten the image. Then I convert the background to transaprent.
85QuickLayout.png
This one was done using snagit, we prefer the torn edge effect. Is this the sort of thing you are trying?
You do not have the required permissions to view the files attached to this post.