Generally, Boeing has attempted to make the interiors of their aircraft as similar as possible, with one "unified" interior across different aircraft (i.e. based on a single "look and feel" for you UX enthusiasts), such as the older (but still fairly new) "Signature Interior" (debuted with the Boeing 777) and the newer "Sky Interior" (debuted on the Boeing 787).
When a new interior style was created, it seems like Boeing generally tries to copy that same interior to other aircraft. For instance, the Signature Interior was also used on earlier 737 NG and later 747-400 and 767 aircraft (with a retrofit offered), and the Sky Interior was used on later 737 NG (conflicting information about retrofits), 737 MAX, and 747-8.
While it seems from the above that Boeing is pushing new interiors onto older aircraft, including the 737, 747, and 767, this doesn't seem to be the case for the 777; even those coming off the assembly line today still have the original Signature Interior. Why didn't Boeing make a Sky Interior for their 777?
To make it clear what I'm talking about, here are some images and descriptions of each interior:
- Middle section overhead bins and passenger service units appear integrated with the ceiling.
- Side passenger service units are angled.
- Overhead bin open handles can only be pulled one way.
- The interior fittings are beige.
Source: Lufthansa Magazin
- Middle section overhead bins and passenger service units appear attached to, rather than integrated with, the ceiling.
- Side passenger service units are almost completely horizontal.
- Overhead bins have open handles that can be pulled either way.
- The interior fittings are white.
Keep these mind's answer points to a Ukraine International Airlines marketing material that advertises the "Sky Interior" for their 777s. However, clicking through the link shows a picture of their 777, but it has the same Signature Interior as above.