Hello Peggy,
When we converted all our lighting to LED, we added some emergency lighting. We used some very simple, small, and inexpensive LED units such as these https://www.1000bulbs.com/product/111322/EM-FHEM10W.html
You'll naturally want to hide them, one suggestion is to let them shine through sheer curtains or other such. They're pretty small so you can use your imagination to put them where they won't be too obvious. One thing you'll have to have is a source of electricity that is not switched (constant hot) so that the lights can charge, and of course, so they'll know when the power is out.
You might consider contacting your local fire department for guidance (or not!).
Good luck. While historic accuracy and aesthetics are important, safety is still job #1.
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Curtis Morris
Exhibits Manager
Shiloh Museum of Ozark History
Springdale AR