The only photos I know can be found here https://nswrail.net/
there's also a small book of the Murwillumbah line but it's not very useful information it also has photos of some stations and a few trains on the line, I can't remember the title of the book itself but I do know I have a copy of it "just can't find it on my shelf as I've packed it away"
, it's pretty cheap at the ARHS shop
Other than that, that's pretty much all I can help you with!
There's a MSTS route of the Murwillumbah line it can be found here if you have MSTS or can get a copyhttps://www.coalstonewcastle.com.au/