artist's impression; imaginary rendering
A picture or illustration created from imagination, not from direct observation. Often used for speculative reconstructions, concept art, or visualizations of things that cannot be photographed.
This artist's impression of the dinosaur is based on the latest research.
An imaginary rendering of the planned building was released.
イラスト is a general illustration, not necessarily based purely on imagination; 想像図 emphasizes that the image is speculative or conceptual.
Compound of 想像 (imagination) + 図 (picture, diagram).