Although the simplest solution for the immutability of data to store everything on the blockchain. It includes images and other files and it is possible to do it too. It is interesting to note that it is not done on practice though. Storing too much data will encumber the blockchain to the point that it will slow down to a standstill and exceed the limits of the hard drive itself. 

Although blockchains like BigchainDB have overcome this problem but they have sacrificed their byzantine fault tolerance. This means that the blockchain has weak security and thus is not as secure are your regular blockchain database.

The solution to our problem lies in using protocols like IPFS that allows peer to peer file transfer without burdening the blockchain in the process. If the the file storage can be sufficiently decentralized than it can bring the presence of large files like images and videos on internet to near immutability.