I am looking for a good resource that explains all the image/file uploads for LimeSurvey, where they are stored, etc. Some are obvious, like to upload an image to a question, you just manage it in the Resources tab for a Survey. Also, to manage the images for a specific theme, you can upload and modify that in a theme editor.

However, for example, on a Survey, to upload a logo or background, the upload options are under the Simple Options and Advanced Options tabs for Theme Options. These are somehow labelled as "Global" in the picker.

The picker for the images (e.g. logo or background image) shows images from Global, Theme, and the Survey (resource tab).

How can the Global images be managed? How can they be deleted? How does the application behave if it cannot find those images? Does it put in a "cannot find image" or does it just show a broken image?

For example, the picker looks like this:

Inherit
Global
banner-wallpaper.jpg
banner-house.jpg
Theme
preview.png
logo_pdf.png
...
Survey
banner-field.jpg

So, the Global ones show are uploaded on Theme Options > Simple or Advanced tabs. But how do you delete them?

The Theme is from the theme and edited there. The Survey is from the Resources tab and managed there.

Thanks.

Global : image uploaded in core theme
Template : image uploaded in Theme
Survey : from survey