These scripts do not require an existing image. They usually create an image themselves. In the past there were several scripts supplied with GIMP that belonged to this category. However, the results all looked dated compared to todays standards and they were not well maintained. Which is the reason that they are not installed anymore in GIMP 2.10.

In case you would like to keep using these scripts, they are still available as separate downloads that you have to install yourself. The scripts and other resources can be downloaded from here.

In the past there was a dedicated Script-Fu menu. Nowadays most scripts and plugins are logically categorized and added to the menu that closely resembles their function. Most of the scripts appear in the Filters menu, but there are also several in the Colors.

Some scripts with specific functions appear in other menus, e.g. the script New Brush (script-fu-paste-as-brush) is integrated in the Edit menu (Edit → Paste as... → New Brush), that is more logical.

	Note
	Some older scripts that haven't been updated may still appear in a dedicated top-level Script-Fu menu.