Hi DDD! I have a mac too I have found that the lights are just used to help you see your way around the house when it is dark, they don't actually wake up the peeps. If you don't like the lights you can of course delete the light files. But they don't do any harm. (If your peeps wake up just drag them back to their bed and they will say "going to bed." Don't put them on the couch though for "taking a nap" as I'm not sure that has as much of an effect for replenishing energy.) But the best option is not to open the game when it's night in your time zone as they will be sleeping as well. They need a full nights sleep to be rested in the morning.
As for the images folder, it's inside the VirtualFamilies.app package, as Lyssaria said; VirtualFamilies/Contents/Resources/images is where you would find it. But make sure you back up the images folder before implementing any mods.