For a RAG project for a client with a lot of PDFs and Powerpoints with images, I used ColPali a year ago. I see the provider ColiVara is still online but it seems to have fizzled out.

Retrieving based on text and then giving the generation model the image instead is much smarter than retrieving based on image. Image-based retrieval is slow and expensive.

Same with giving the model an image vs a structured representation of it.