The pre-Toyfair catalogue for 1986 shows off a number of Transformers prototypes, including the combiner groups and city commanders.
The catalogue was on ebay, and now bought by the allspark website, and when they get it, they'll post up decent scans. The auction itself only posted up a sample of small images, which included 3 of Transformers (there might be more TFs pages).
Doesn't look like the allspark page actually posted up copies of the ebay images, so check out the seibertron news post here for those 3 ebay images.
Interesting to note that the Galvatron had to have a yellow barrel, probably for safety laws.
Superion's bits were originally blue (except the feet).
Onslaught has some odd colourings.
And some of the combiner figures appear absent of stickers, which may have been typical of prototypes... or added later as they look a bit bland without them.
Will update when the full scans are posted somewhere.