This is a reconstruction of a Doom poster seen in a photo of Id's offices. The poster features a red demon face set against a black background, a large version of the image that appeared on the cover of the "Ultimate Doom" box. The poster itself apparently was never commercially available, implying that the poster in the Id photo was a one-off one-of-a-kind print.
This is a high quality file suitable for printing as a poster at a print shop. As a result, the file itself is very large.
I (fraggle) am uploading this to the idgames archive; Peter Heinemann gave me this file to host several years ago as he needed web hosting for it. His original description of this file is included below.