In your social media content table, you would want to create a "linked record field" to link to the assets that you want to link to.
Then, in your social media content table, you would create a "lookup field" that would lookup the images from the assets table.
Note that the images would still live in the assets table, but you would be able to see them in the social media content table.
If you'd like to learn more about linked record fields and lookup fields, I cover these 2 topics in my free Airtable training course, which you can take for free by signing up for a free 30-day trial with LinkedIn Learning.
p.s. If your company has a budget for your project and you’d like to hire an expert Airtable consultant to help you with any of this, please feel free to contact me through my website: Airtable consultant — ScottWorld
If you're not worried about historical data, you can just link them up and use lookups
If you're worried about historical data, then you'd want to have an "Attachment" field in the social media content table and have an automation update that with the linked record's attachment