Themes

It's usually easiest to just copy an existing theme first:

Inside /theme dir: cp -R oldtheme newtheme

Inside new theme dir:

find . -iname '*valid*' -exec rename 's/old_theme_name/new_theme_name/i' {} +
find . -name '*' -exec sed -i -e 's/old_theme_name/new_theme_name/g' -e 's/Old_theme_name/New_theme_name/g' {} \;

Please note that the second line searches for two patterns: one with a capital and one without.