A theme typically consists of a set of configuration files, Velocity templates that include HTML, JavaScript and CSS files and image assets. This allows to customize the functionality and style the looks of your viewports to fit their purpose.

This great amount of flexibility must be handled responsibly and thus the editing of theme resources is restricted to Confluence administrators by default.

Space administrators can configure viewports in their respective spaces including picking a theme.

Furthermore they can customize the settings and upload image assets for viewports using the Help Center Theme. Specifically this means they can customize the theme settings and upload image files in the formats PNG, JPG and GIF.

Extend theme editing permissions to space administrators 

If you need to extend the permissions to configure and customize viewports to users that are not Confluence administrators, a Confluence administrator can designate one or more groups of space administrators for these tasks.

To do so go to General Configuration > Scroll Runtime > Advanced Plugin Settings and Edit the setting restrictThemeEditingToGroups.

The following options exist:

1(empty)This is the default setting and does not allow space administrators to edit themes further than described above.
2groupname1,groupname2This extends theme editing permissions to users that are members of the given groups and are space administrators. As a user is only space administrator in the scope of a specific space this also means that they can edit themes only if they are used in these spaces exclusively.
3*This special value allows all space administrators to edit themes in the scope of their respective spaces. (This was the default setting before Scroll Viewport 2.20.0).

In most Confluence versions the default permission settings allow every Confluence user to create a personal space. The users would then be space administrators of these spaces and can edit themes there if option 3 is used.