Looking at this from a creative point of view on the flags forum myself and others have been discussing designs for the flag of the 'Northern Isles country'
The two Islands groups are culturally and historically linked. They both share a mixed Viking and Scottish heritage and culture. I have even recently discovrerd my family name originates from the Viking settlements on the Northern Isles. There are also traces of Pict and Geal ancestry too.
Both the individual island groups have their own flags (both crosses)
Flag of Shetland
Flag of Orkney
I proposed of combining them into one in a similar way the Union Jack is a combination of flags:
Civil and regional flag
Merchant ensign (if they remain in the UK)
This idea was picked up by Leonardo Piccioni who designed another perhaps better combination design:
I also thought about defacing the St Andrew's Saltire with a logo, symbol or coat of arms. I came up with the fallowing designs:
I also thought about topping them with a Scots Crown. The thing with these is that they give the impression of being part of Scotland (which they are at the moment) or they represent one culture identity or background(with the exception of the brooch which is not the best symbol) Leonardo suggested changing the field to white and the cross to blue as is done in the Novia Scotia flag. He made a St Andrews cross version based on this and a badge from 1969 commemorating the Island's transition to Scottish rule.
(designed by Leonardo Piccioni)
The cross still represents Scottish heritage and identity but is distinctivly different from the flag of the independent Kingdom of Scotland (again these are only if the Scots vote yes) and the ship represents Viking heritage. The discussion and designs are still going on to view them on the flags forum click here. To see a similar post on Leonardo's blog click here.