maybe not the nicest way to do it, but here is how i would tackle the issue (i used a similar approach, albeit not with jevois <-> arduino)
On jevois/python side, you convert the open cv image to a jpg byte array, then to a base64 string. Finally dump the image on the serial link like this:
Then on the arduino side, it shouldnt be very hard to decode that back to raw values to be written on a file on your SD card.
I do not have a JeVois cam nearbyt to check python base64 support with bundled libs, but i think the following code should work out-of-the-box
C:\Users\user>python -c "import binascii; data=b'use raw bytes of your jpg here instead'; print(binascii.b2a_base64(data).decode('ascii').strip())"
Do keep in mind that using base64 will likely add 33% of extra bytes on your serial communication link compared to raw binary. It's unlikely you will get realtime stream. dunno if those limitations suit your usecase. At least that's how i would handle it.