I like the idea, but definitely make it untradeable. It is a reward, a trophy, not something you can try to sell for. Also, how hard would it be to customize your own icon though? Would it need to be done and paid for by a gfx? Don't want a bad looking one.
My suggestion:
Have there be an icon for every donor listing from lowest to highest. They're still supporters of Sythe, whether they are huge donations are not. They are still in the donor's column.
$50 donor and $100 donor barely have any perks. I'm sure people would like to start off at Sythe, make some profit off the market, invest into donor $5,$50,$100 and have an icon to catch their eye on as a encouragement to get to the higher donors.
Why not have an Icon that Says Sythe Proud , with money or coins on it. from small coins to bigger coins. If it's runescape related it'd be easier to have but that's biased so no. If it was have coins animation in 1gp > 100 gp> 1k gp> 100k gp> 1m> 10m > 2147m .
Or if you can just create an icon that shows money in form of bigger liquidity.