Juat like magnets

I think it's because you're uploading images that are way too big for the thumbnail generator to handle. I'm assuming that when you first upload an image, you immediately go and hit "change submission file" to upload it in full resolution. On that page, I would make sure to uncheck the "Rebuild the thumbnail from this file" box first and foremost, and if you're still not getting a proper thumbnail then I would wait a few minutes before uploading the full res image to make sure that the server has time to generate the thumbnail from the low-res version it creates.

To fix your existing submissions, I would try creating a downsized version of the images, changing the submission files to them with "Rebuild the thumbnail from this file" checked, seeing if that does fix the thumbnail, and then changing it back to the high-res image with the box unchecked.

Personally, I would recommend against uploading your images in full resolution anyway, as your images are massive and hitting "full view" on one of them on even a 1080p monitor makes it so you can only see a small portion of the image at a time. I like to leave my submissions at FA's preferred maximum size and upload the full-sized images somewhere else. I then link to them in the description and that way people can see the whole image without it ballooning the page out of control while still having the option to get it in a higher resolution if they want it.

I'll give that a shot. I suppose uploading a more 'reasonable' size is probably best as well, but I do think that some people tend to enjoy macro pieces in particular when 'hyper-zoom' is an option. I probably will have to keep a secondary upload site handy for the ultra-high resolutions, but I ultimately was a little hesitant to upload the art that I get anywhere else as the majority of it is kink stuff.

I've found that Discord actually works well as a sort of image hosting archive. If you have a friend you can trust or an alt account, you can upload pictures via private message and get URLs for them that other people can access. As far as I can tell, the links don't ever expire, so that's what I like to do.

This was really good advice. Thumbnails are working now.

Thanks a bunch for your help.