Your brand is important.  You want to be consistent throughout all the collateral pieces you share so brand recognition remains strong in the marketplace.

It's not just office stationary, its part of your brand. They must be functional and attractive, consistent and complimentary, and coordinated with the rest of your organization's branding. 

Your business cards and letterhead are part of your marketing collateral and must fit the part. So ensure your brochures, website, and other pieces use consistent fonts, complimentary color schemes, and imagery.