Thanks for pointing me in the right direction. I can disable previews in Dolphin which is my file manager, but I'd love to keep image previews in general. I'm pretty sure veracrypt for windows disabled thumbnail creation automatically for veracrypt mounts, but don't quote me on this.
When I used Veracrypt in Windows, no thumbnail images were created for files opened in a container if I remember correctly. However, in Linux this does not seem to be the case. Is it somehow possible to disable thumbnail creation in Linux for photos in a verycrypt container through some Veracrypt setting?