I presume you're thinking of printing this on a work printer??
I don't know how much a full colour a0 image would be to print exactly, but I bet it wouldn't be too far off the cost of a poster
BTW.....'royalty free' / 'free'??
There are loads of 'royalty free' image libraries out there (Google will turn up loads) but that's not the same as 'free'...all it means is you don't have to pay when you use the image, but normally (and especially for large res images) you'll still have to pay for the image file itself...this often runs to several hundred pounds for a good image that will blow up to that size
I suspect that you probably won't find many images that are nice enough to want to use in that format without having to buy them
Aye, I've just had a net rummage and realised what you have just pointed out. Royalty free doesn't mean the same as free! Learn summat new every day eh!? As for the size, without going to a specialist I'm never going to get anything that size now I think about it am I! I'll have to brush off my image editing skills and see what I can come up with.
Thanks for your input
Fooooound some! Here. Proper massive Hubble images. I'm downloading one now that is 7.8M high by 3.85M wide "Stellar spire in the Eagle Nebula" I think my PC might fall over before it completes though