Deep within Apple's mobile operating system is a stock feature that you can use to disable touch on the screen, so that you no longer have to worry about someone sneakily swiping through your Camera Roll.
Step 1: Enable Guided Access
Go to Settings -> General -> Accessibility and scroll down until you find Guided Access. In the Guided Access settings, enable the Guided Access toggle. This setting will allow you to control which features are available in a single application, like the Camera Roll.
Once that's turned on, enable Accessibility Shortcut at the bottom, which will turn on the Guided Access feature anytime you triple-click the Home button on your device.
Step 2: Configure Guided Access
Now that Guided Access is easily accessible, head over to your Camera Roll and find a picture you want to show someone. Triple-click the Home button and wait for the Guided Access window to pop up.
At the bottom-right of the Guided Access window, select Options. Switch the Touch setting off in order to disable any sort of screen touches or swipes. Select Done and tap Start at the top-right corner.
Now you'll need to enter a passcode, which you'll use later to disable Guided Access. Enter it twice and a short-lived message will then appear saying "Guided Access Started".
Now hand your phone over to your friend or family member and watch them try and swipe left or right to no avail.
Step 3: Disable Guided Access
Once you have your phone back comfortably in your hands, it's time to disable Guided Access. Once again, triple-click the Home button, which will bring up the Enter Passcode screen. Enter the passcode you used earlier, which will then take you to the Guided Access window once again.
Tap End at the top-left corner and a "Guided Access Ended" window will pop up, indicating that the feature is now disabled.
Hopefully this will dissuade your friends and family from trying to look through your photos when handing over your phone. Eventually, you might not even need to enable this feature, conditioning everyone to not be so freaking nosy.