What files can I upload and whats the size limit?

For the private downloadable file: any and all file types are supported.
Size limit: 3GB (including preview file)
For the preview images: any image file, mp4 or .GLB
Size limit: 200MB
We recommend the preview images dimensions to be larger than 800px x 800px.

MP4s and GLB (3D files)

If you want to have a 3D image that can be interacted it by anyone - you just need to upload a .GLB file as one of the preview images.
MP4s are also accepted as a means to play videos if the user wants to watch it.
You still need to upload a basic image as the display image if you choose either of these types.