It would look terrible, because I can't draw.
Proper answer - It would probably need to have something linked to the country this new nation was previously a part of (assuming that I'd founded this country out of something that was before a part of another country, rather than claiming a piece of rock in the sea or something).
The most likely place I would get away with claiming would be my own bedroom. The flag would mainly be Blue, then, for two reasons: one is that my bedroom is painted Blue, so with most of the country's geography being blue it would make sense; two is that Blue is the background colour of Scotland's flag, of which my country was formerly a part of, so a Blue flag would link the country to Scotland's heritage.
For items on the flag, I think it would need to display something that was recognisably a part of the country's culture. I'm thinking it could have a computer in the top right corner, because mostly what I do in my room is use the computer.
It can have a red stripe somewhere, too, because I quite like the colour.
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How many lightbulbs are there in the room you are currently in?