Hydrofracking background image [#53912853]

New image for background in Hydrofracking theme. This is far too big in terms of file size, however; we need to scale it down.

https://www.pivotaltracker.com/story/show/53912853
Replace Hydrofracking SVG background with PNG

[#53912853] This uses a smaller file-sized PNG for the background.

https://www.pivotaltracker.com/story/show/53912853