I've not heard of fim, but fbi can be installed.
sudo apt-et install fbi
Do you need to retain each image, or can you overwrite each one as you go along?
I've been looking at fbi and there doesn't appear to be a timeout option on it. You might need to 'kill' it after the required time. Not sure how to do that in bash, but there is certainly a way.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
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