I am a Realtor for 25 years. First you need a Real Estate license and pay your dues to the NAR, and to the state real estate organization and next to the local board and next to the MLS. Do you want to do that, an amount of close to $500. Next you can only upload the pictures of your own listings or if you are an assistant to a realtor. A Realtor is not allowed to give his id and upload code to any other person. Doing this he/she might loose their license.
No, you better forget that approach.
Uploading the photos happen during the same process as putting the listing informations into the MLS. Believe me there are many Rules and Regulations and an agent who does not follows the system ends up paying a hefty penalty.