We have now added the helpful dialog that asks if you wish to save unsaved changes when quitting.
However, this does not apply to images that have been modified inside of Blender. If you have an unsaved image, or changes made via texture painting, changes to said image won't get saved.
A lot of users have reported this problem.
We could solve it by either:
- Always saving images when you save the blend file or
- Adding a prompt, asking users to save unsaved changes to images.