This is what I know very much. I don't know where the Satoshi Nakamoto designed this and that is coming from. I think we are just stock with what has been popular enough to gain a foothold and it sticks. There isn't any much meaning attached to that other than a gold shiny coin with a big stroked B. Which I presume,

Gold colour just hinges on the nature of Gold which is attractive and valuable.
Coin remains a nature of ore money and
BTC remains the currency been referred.

There isn't anything much about these. Let the logo thing go and instead, just buy some bitcoins.