The graphics, CG and compositing work is exceptional, read the article in CG Society for lots of detail. It is still remarkable to me how seamlessly complex the digital work is on films of this calibre. We are treated to whole shots where digital characters, environments and cameras are flailing around and giving us a remarkable view of these imagined characters.
With a comic realisation there is always a good chance of some groovy concept art. Here are a few source sites and examples: Ed Natividad on ConceptArtWorld ; Aaron Sims, Eddie Yang and George Hull on ScreenRant and Josh Nizzi on ConceptArtWorld.