I took a few intellectual property classes back in school and its pretty ridiculous what people try and have protected.
Tiger Woods once sued a guy for painting a picture of a guy playing golf that looked somewhat like his form.
From what I remember though, there was an artist that used a whole bunch of brand trademarks like Starbucks etc and won the case because it was artistic expression.
Maybe you should create a piece of art that has their logo and pictures of money and then you could proudly display it in your artwork/payment processors page.