Fathom, the trade mark as you call it is only registered to people (e.g. Holder in the UK) for the purpose of making and selling motorcycles. I believe ( & I was wrong once so I could be wrong again) the Vincent Scroll and HRD logo can be reproduced on such things as T shirts etc. without infringing copyright. One of the lawyers out there can give a definitive answer. As far as Mr Li goes, his rights only applied to the USA and possibly a couple of European countries. You have to choose whether you want to photograph "real" bikes, warts and all, or photoshop them to appear to be something they are not. Unless you are seriously au fait with Vincents then you could be entering a minefield. Most of the bikes the collector has were purchased as going machines that had been "restored" or were "original". There are probably only a half a dozen truly original bikes out there so best to take good photos of what you see rather than cock it all up. There are books out there that show what some models should look like and you can't do much better than rely on Jacqueline Bickerstaff's excellent tome. The person's that have been advising (?) on the collection have used their own interpretation and recollections: if you ask 6 Vincnet people for an opinion you will receive 7 answers, all of which may be correct!!!! With 35 mm photography I always thought an 85 mm lens gave the best results for bikes....
