the "models" section is made to build default avatars for new users grid registration.
this is usefull to don't have ruth or a cloud when new users are registering on the grid.
1/ create some avatars inworld and dress them
2/ add their uuid in the ui users admin page
3/ add an url to the picture that will be displayed to show the avatar on the registration form
4/ when a user is using the grid registration tab to create an inworld avatar, the user will see the pictures and will be able to select an avatar as a model
5/ when creating the account, d4os will simply clone the avatar model's inventory to the new user inventory