The first issue is causing the rest of the issues. There is no validation in this version so if you add an image that has failed to upload the actual image then it will still add to the database just without the image. That is why you are getting blank thumbnails and the blank image. And the first problem could be a lot of things, this alpha wasn't tested very much as was made on an early version of XenForo. "Loading..." should mean it has uploaded the image and is loading the image into the browsers cache before showing it to you. Next version sees a lot of code refactoring and a more finished product that I can support. I have had barely any time to get my work done so haven't been able to finalize the beta (it only needs permissions added and a couple functions finished). I am almost done with a couple clients so should have a lot more spare time soon. This week if possible, if not the second week of April.