A few weeks ago I went to see Blade Runner: The Final Cut in a one-off showing at the Tyneside Cinema. I've only watched the Final Cut once and that viewing was a bit compromised, so it was nice to see it properly, and on a massive screen with decent surround sound too.
Whilst watching it I saw something that I thought might potentially have been a visual reference to Scott's earlier movie, Alien. When Deckard is climbing onto the roof of the Bradbury building, there's a decorative motif that to me, looks very Giger-esque, biomechanical, a bit like a chest-burster.
I went back and took a screenshot from the Blu Ray at the same point. What do you think?
As it happens, whilst the inner regions of the building in the movie are the Bradbury building (or at least the entrance hall), I don't think the upper exterior shots are.
There are a few other, well-known references to Alien in Blade Runner, although they are likely simply re-used effects rather than explicitly easter eggs. The display screen in Gaff's Spinner is re-used from the Narcissus (here's a comparison) and the ambience in Deckard's apartment also featured in the Nostromo's medical bay. Some enterprising person has put together a 12 hour session of that particular sound effect looping. There's a number of other comparisons and spots at this propsummit.com thread.