I’ve just published on GitHub an improved versione of the Facets plugin, originally developed by https://github.com/AR2L.
The plugin allows to refine Items browsing via a block of dropdown lists of available values. List of elements is now fully configurable, as it sorting order and other details.
I’ve submitted a pull request to the original developer to merge the code; in the meantime, if anybody will have a chance to further test my version and report possible issues, that’d be really appreciated. The improved plugin version can be found at https://github.com/DBinaghi/omeka-facets-plugin.