Not picking up all pictures?

Hrm. I can't think why feh would skip any images..

One thing you could try is dumping the filelist, to see if feh has picked up the whole tree. Just hit f (if you can in your picture frame) to write it out. If you can't hit f, you could use the --filelist /tmp/mylist option and feh will write it out when it exits.

If you are patient, you could also just add --list to your command above and redirect to a file. This will take a while as feh will attempt to open every file in the tree, the output should contain image info, or if for any reason feh doesn't load the file, an explanation as to why.

feh --list -zZFr -D 15 --hide-pointer /pictures > /tmp/feh.out 2>&1

Listing shows what's expected (all files seen).

However, I have a theory on what caused this. As I mentioned, /pictures is nfs mounted. And connectivity is via wireless. My wireless router goes down every now and then (don't really know how often, perhaps every other day for 5 or 10 mins, maybe a lot less, maybe a lot more).

My theory is that during times of no connectivity, feh attempts to display a picture, and when it can't retrieve it, it notes it as not available and doesn't attempt to retry it for the duration of it's lifetime. So, the pool of displayable pictures diminishes every time I have an outage.

Assuming this is the problem, I've added the --cycle-once parameter to feh, and set it in a perpetual loop, i.e.

while [ true ]; do
        feh -zZFr -D 15 --hide-pointer --cycle-once /pictures
done

My 4k pictures should cycle through in about 24 hours (I have the duration set to 15 secs). So, any outage problems should be "reset" once per day.

Is this theory plausible? Thanks.

Yep makes sense - if feh tries to load a file it scratches it from the filelist and goes onto the next one. Using cycle once as above would sort you out, as would a feature to rescan the directory occasionally (planned).