Welcome to Android Central! The Gallery or Photos app will show any image saved in storage, regardless of the folder, unless there is a ".nomedia" file in that folder. Smart coders will include the .nomedia file, but some just don't think about it. You can add one yourself--use a file manager app like ES File Explorer, and create an empty file called ".nomedia" (make sure to have the period in front) in the folder that you want the Gallery to ignore.
If you still see those images after creating the .nomedia file, then go to Settings>Apps>All, select Gallery, and Clear Cache/Data, then Force Stop. Now open it again, and wait a few seconds for the database to rebuild. Those images should now be gone.