The Google Search Images page only applies a dark theme to the page header, not to the search results. The search results page on ipv6.google.com remains unchanged.

can thare be a switch to turn it on and off

Very good, however there is one issue. After searching, when I click on google's logo in the top corner and return to the homepage there dark theme stops.

Really nice theme. only issues I've noticed so far is that under the "news" tab the main title text is still black text so its hard to read, and that under the "shopping" tab there are still some white UI elements. Otherwise thanks for the extension :).