Creating a ZIP like collection on Runtine

I am currently working on a game, where the player can load images from a folder into the game, and it works quite well. How it works currently is that it loads the image from the given path and saves the path in a string array. That string array is then saved and when loading next time, it goes through and loads each image's path. However I would like to enable these images to be uploaded onto a server and make it shareable that way. (Uploading is not the main issue here, I know how to do that already). I thought that it would be better if I uploaded them as one big file rather than potentially hundreds of individual files. I also image that that would allow for easier caching and loading locally, without the trouble of dealing with images that were deleted in the folder.

Is there a way to put a series of Textures (loaded images) into one collection and save it? (I was thinking AssetBundles at first, but it seems they cannot be created on runtime, and if they can, then I am missing it).

If not, how do you think would be the best way to approach what I am trying to do?