Can users choose from a list of themes?
Let's say the administrator created more than one number of themes from the Nuxeo Studio branding section.
From the created and saved themes by the admin, is it possible for users to choose from them depending on their preference?
If so, where is the list found or how can users do that?
If not, then what is a good alternative or solution to making it possible?
There is no notion of theme per users in Nuxeo: we only have a notion of theme by space (or workspace). You can take a look to the documentation here: http://doc.nuxeo.com/display/USERDOC/Applying+a+Preset+Look+to+a+Space
You can make a try with the marketplace addon Unicolor Flavor: it displays a list of themes in the Theme Local Configuration when a user is an administrator of the space. Unicolor Flavors Set The documentation is here:http://doc.nuxeo.com/display/USERDOC/Unicolor+Flavors+Set
When you can create many brandings in Nuxeo Studio, the default one will be applied, and the other ones will also be available in local configuration.
I edited Lise's answer: additional brandings (non-default ones) created in Studio are available in local configuration.