New-PnPTenantSite : LocaleId 2057 is not a supported locale.

When creating a site collection you can only specify a limited number of LCID's (corresponding to the available language packs for SharePoint). After the site collection has been created you can further finetune your regional settings using CSOM Web.RegionalSettings for example or via PowerShell as described in the following blog

http://consulting.risualblogs.com/blog/2016/04/08/sharepoint-online-csom-update-region-settings/

This MSDN article lists the LCID's supported when creating a site collection

https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.splanguage.lcid.aspx

Hope this helps