Per voting and policy (http://es.wikibooks.org/wiki/Wikilibros:Propuesta_de_pol%C3%ADtica_de_im%C3%A1genes) the es.wikibooks community decided to dissable local uploads of files in favor to upload them to commons as the Spanish Wikipedia did before.
In addition: the link on the toolbox "Subir archivo" [[b:es:Special:Upload]] (upload file) must link to [[commons:Special:Upload]].
Thanks for your help.
URL: http://es.wikibooks.org/wiki/Wikilibros:Votaciones/2009/Pol%C3%ADtica_de_im%C3%A1genes