I agree Viggo Mortensen and Stellan Skarsgård would be interesting guests.
Another actor of Danish heritage (paternal grandparents were Danish) that might be interesting is Michael Madsen, who played the parts as Bill's brother Budd in the Kill Bill movies. Tim Roth would also be an interesting name, if he attend conventions.
From Star Wars minor characters like Bib Fortuna (Michael Carter), Admiral Ackbar (Tim Rose), some of the Imperial officers (eg. Veers (Julian Glover), Needa (Michael Culver), Piett (Kenneth Culley) and Jererod (Michael Pennington)) would be good names. Silas Carson (Ki Adi Mundi and Nute Gunray) and Leeanna Walsman (Zam Wessel) would be awesome, as they are very rarely seen at conventions.
Finally I have to suggest Bud Spencer and Terence Hill, cult classics from my (and many other Gen-Xer's) childhood.