I disagree about the image not being fine. We were printing table tents, cooler tags and shelf talkers for a local liquor distributor, scoring them on our Summa (roller table front and back), then peel them out of the styrene . Full color, some with photos and you could scrutinize them.
They eventually bought an Oki Data and brought that work in house. What we gave the client looks as good or better than what they print.
Wanted to mention that if you need a photographic image and your running Onyx, get the PVC 10 profile from Grimco. Really nice print, but slow.