Conclusion: it can become an interesting project, but it may be better to not be linked to the idea of photos, it may be better with (any) actual files. It avoids confusion and other possible problems.
The problem remains that any tiny change to the file in question will radically change the output of the hash and therefore generate a totally different wallet. With no checksum or error correction built in, it then becomes essentially impossible for the user in question to recover their wallet.
You use a bunch of photos to generate a wallet, great. You then decide to back up those photos to a USB stick, but your OS didn't copy all the metadata. Wallet lost. Maybe you back them up to some cloud storage, but the cloud storage automatically converts them all to .jpg or to a standard resolution or changes the metadata to attach the name of their service to the photo somehow. Wallet lost. Perhaps you do something as simply as rotate or crop one of the images. Wallet lost. This is far easier for an average user to get wrong than writing down a seed phrase.
Using any other files still poses the same risk from all the metadata that most average users don't even know exists, plus opens the door to using very insecure "entropy", such as a .txt file of some famous quote.