There have been many attempts over the years to categorize UFO and ETs based upon eye witness accounts. The sources below vary from an alleged Government documents to amateur researchers

An interesting compilation of UFO shapes from 1948 to 1967. Drawn by Knut Aasheim

Two photos from an alleged US Gov document dated April 1954, within the document on page 20 is a section depicting four UFO shapes : disc, cigar, cone and triangular. I find the triangular one very interesting as that shape has been really popular since the 1980s but was obviously flagged up by the US Government back by the early 50s. Notice the light in each corner and the centre light which matches so many descriptions from around the world

With some humour, numerous reseachers have produced compilations of ET appearance based on eye witness description