I don’t know Lemmy well enough to advise on that side of things, but you can share multiple images via one link using an Imgur.com album for example. Hope that helps. :)

Upload the first one using the upload button, then post the rest of all in the body content, there is a image icon button for you to upload the images to the body content.

To save space, after uploading the first picture, you can embed all the others if you have uploaded them elsewhere, I did that for a post since I had previously created a Thingiverse page, I just took the image link and used it in the body.