imac7 crashed and now I'm stuck! Help!

I have an iMac 7 running Maverick. when I turned it on this morning I got a grey screen constantly starting up but with grey/white black pixelated short lines: Flickr pic here (this site won't let me upload for some reason): https://flic.kr/p/tMoa5e

I've done the usual stuff, restarted, tried resetting the PRAM etc, unplugged all the peripherals with no joy. Then I hit google and followed the suggestion of re-booting in single user mode so i now have this: https://flic.kr/p/sQg7ub

Except now its got a load of flickering lines on the screen. I've rebooted it because the instructions I found here: Re: OS X Mavericks installations fails after reboot, stuck. Safe mode does not help which looked like it might be the answer were not clear enough for me (I am not a computer genius by a long stretch!).

Basically it is stuck in a cycle of rebooting itself and going nowhere. I can't find the original start-up disk and I just don't know what to do. My other half's photos are all on there and he's starting to panic about losing work.

Any help?