The majority of the images I have used in my LOs were on a CD I purchased in the States & they only have numbers as file names.
From this I take it that they were always 'free to use'.
Hope so or I'm in big trouble...!!! LOL
I have previously downloaded prints/posters from the web from a 'free' site. Likewise, artist's name is not always mentioned and when it is, I do give credit. In these sites, when you right-click the print there is quite often a restriction on downloading ~ so obviously YOU CAN'T. I assume therefore that the others on the same site which enable download can be used freely...!!**!!
When I've found an artist's website I REALLY like (eg. BORG) I email & ask permission.
Would welcome comments, pls.