Have you tried changing the storage location? Also, are you restoring your gallery each time you try a new ROM? You could have the folder hidden on accident and as you restore the gallery that folder becomes hidden again. See if you cannot find the photos another way, for example: Quickpic or ES File Browser.
HTC One M8: 1.54.654.13 Rooted Stock De-Odexed -|- Firewater S-off -|- TWRP: CTB's 126.96.36.199
HBoot: 3.16.0.0000 -|- CID: 11111111 -|- PRI: 2.28_003 -|- PRL: 51101 -|- Radio: 1.08.20.0610