Best practice to remove design package in SharePoint 2013?
Best Practice is to not do it - as Microsoft doesn't support it.
"In SharePoint 2013 you cannot uninstall an imported design package, and you should never attempt to deactivate a design package through the solution gallery. If you do, page layout content types are removed and users may not be able to create subsites"
You may be able to work around this restriction if you export the page layout content types first, remove the custom ones, uninstall the package and then re-import the content types. I've not tested this method however.