If you are going to do it that way just embed the info in a legitimate image using something like this:
https://pypi.org/project/cryptosteganography/Many other options available to do it.
Even if someone looks through every image it still will not matter unless they try to decode / decrypt every image.
I really don't think anyone is going to bother going that deep unless you are on some list. And if you are it probably does not matter anyway they already know what you have.
-Dave
As DaveF mentioned, steganography techniques can be more interesting than other complicated methods, but before hiding a message as a seed in an image, you won't do it with a bare seed without protection, you can add a passphrase, but I wouldn't do that in this case.
One of the techniques I've been studying is
seed-otp, which consists of creating a multifactor authentication key, this key combined with your mnemonic phrase creates a new list of words indistinguishable from your original mnemonic phrase, which is nothing more than your encrypted seed, but instead of the encrypted output in cyphertext with a sequence of unreadable random bytes, this method uses words similar to the BIP39 wordlist to encode your original mnemonic phrase. You could stop here, but you would still have to explain to the customs guard why you still carry a list with 12/24 words (if this ever really happens, the chances of it happening I believe are very low).
With the mnemonic phrase encrypted by seed-otp, you can load this information into an image by embedding it and optionally inserting a password. There are several applications that fulfill this function, one of them is
OpenStego (I haven't used any others). This way, you can save the image that carries the secret of your encrypted wallet on your smartphone, pen drive or any other media device that carries images. This way, there is no way to suspect a simple image, even if you inspect your device (I've never seen this happen).
You must remember your OTP key responsible for restoring the mnemonic phrase to its original state. To do this, you can save this key in a keepass file or another password manager of your choice or write it down on a piece of paper, since it won't draw attention in the same way as a list of words known to be a bitcoin wallet mnemonic.
Here is an example step-by-step:
1st let's say you create a new mnemonic phrase or use an existing one, download the html file from the
seed tools page (the process is similar to iancoleman), after everything is ready, create or insert your recovery seed:
2nd Go to "Select a Bitcoin Tool" and select the "One Time Pad" option, below there will be a "One Time pad key" field containing an otp key, if you prefer, you can generate a new otp key by clicking on "New Key".
3rd After creating the otp-key, click on "encrypt" and a new list of words similar to a mnemonic will be created, it is nothing more than your encrypted mnemonic.
Ex:
My original mnemonic:
auto pelican midnight initial barrel kitten aisle rate proof leader point private
My otp-key:
AAwFIAN4AwUCxQaTBhcEsgHmBe8EagHsAVdVUxlP
My encrypted one time pad seed:
receive bacon unfair smart topple dilemma orbit upon health armed tooth stock
It is essential that you know the original mnemonic, have it written down or memorized (regardless of the method, memorize your mnemonic in addition to having it written down), save the otp-key and the one-time-pad encrypted seed so that we can test it and verify that it returns to the original state of your seed upon arrival at the airport and at your final destination.
To do this, reload the page, select "one time Pad" again, paste your otp-key in the "One Time Pad Key" field, paste/type your mnemonic phrase encrypted by One Time Pad and click "DECRYPT".
The final result is your original mnemonic phrase
