To reveal hidden files just type in your cli: unzip hidden.jpeg. One of the packages you can use for more options like more compression options, file extensions and encryption is steghide for linux, but I haven't used it myself. There are methods for identifying hidden files, so if you use steganography make sure to encrypt files first (using PGP, for example) and don't hide too large files so it won't be obvious that something is hidden (for example 500x400 image with 50mb size)