The documentation give clear instructions for installing and setting up a Lemmy instance, but it doesn’t really tell me what I need to do so beyond the implication that I need some computer running Linux.
I have a QNAP NAS device which is running a flavor of linux; how much storage space is recommended for a public instance? Do I need my own website?
You need a domain as well. Not much storage space is needed, 50gb is plenty.
If I were to create Communities around art/photography, am I correct to assume that all those image files would be living on my instance’s storage?
You are correct - it will live on the instance it is uploaded to and federate out to instances subbed to it
I am not exactly sure, but I believe that an image file is hosted on the server of the person that posts the image!
So no, your server would only host the pictures that you and your users post, others might land in cache but can be cleaned.